<glossentry xml:id="acl">
<glossterm>ACL</glossterm>
<glossdef>
- <para>Access Control List - An extended attribute associated with a file which contains authorization directives.</para>
+ <para>Access control list. An extended attribute associated with a file that contains
+ enhanced authorization directives.</para>
</glossdef>
</glossentry>
<glossentry xml:id="ostfail">
<glossterm>Administrative OST failure</glossterm>
<glossdef>
- <para>A configuration directive given to a cluster to declare that an OST has failed, so errors can be immediately returned.</para>
+ <para>A manual configuration change to mark an OST as unavailable, so that operations
+ intended for that OST fail immediately with an I/O error instead of waiting indefinitely
+ for OST recovery to complete</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>C</title>
- <glossentry xml:id="cmd">
- <glossterm> CMD</glossterm>
- <glossdef>
- <para>Clustered metadata, a collection of metadata targets implementing a single file system namespace.</para>
- </glossdef>
- </glossentry>
<glossentry xml:id="completioncallback">
- <glossterm>Completion Callback
- </glossterm>
+ <glossterm>Completion callback </glossterm>
<glossdef>
- <para>An RPC made by an OST or MDT to another system, usually a client, to indicate that the lock request is now granted.</para>
+ <para>An RPC made by the lock server on an OST or MDT to another system, usually a client,
+ to indicate that the lock is now granted.</para>
</glossdef>
</glossentry>
<glossentry xml:id="changelog">
- <glossterm>Configlog
- </glossterm>
+ <glossterm>configlog </glossterm>
<glossdef>
- <para>An llog file used in a node, or retrieved from a management server over the network with configuration instructions for Lustre systems at startup time.</para>
+ <para>An llog file used in a node, or retrieved from a management server over the network
+ with configuration instructions for the Lustre* file system at startup time.</para>
</glossdef>
</glossentry>
<glossentry xml:id="configlock">
- <glossterm>Configuration Lock
- </glossterm>
+ <glossterm>Configuration lock </glossterm>
<glossdef>
- <para>A lock held by every node in the cluster to control configuration changes. When callbacks are received, the nodes quiesce their traffic, cancel the lock and await configuration changes after which they reacquire the lock before resuming normal operation.</para>
+ <para>A lock held by every node in the cluster to control configuration changes. When the
+ configuration is changed on the MGS, it revokes this lock from all nodes. When the nodes
+ receive the blocking callback, they quiesce their traffic, cancel and re-enqueue the lock
+ and wait until it is granted again. They can then fetch the configuration updates and
+ resume normal operation.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>D</title>
<glossentry xml:id="defaultstrippattern">
- <glossterm>Default stripe pattern
- </glossterm>
+ <glossterm>Default stripe pattern </glossterm>
<glossdef>
- <para>Information in the LOV descriptor that describes the default stripe count used for new files in a file system. This can be amended by using a directory stripe descriptor or a per-file stripe descriptor.</para>
+ <para>Information in the LOV descriptor that describes the default stripe count, stripe
+ size, and layout pattern used for new files in a file system. This can be amended by using
+ a directory stripe descriptor or a per-file stripe descriptor.</para>
</glossdef>
</glossentry>
<glossentry xml:id="directio">
- <glossterm>Direct I/O
- </glossterm>
+ <glossterm>Direct I/O </glossterm>
<glossdef>
- <para>A mechanism which can be used during read and write system calls. It bypasses the kernel. I/O cache to memory copy of data between kernel and application memory address spaces.</para>
+ <para>A mechanism that can be used during read and write system calls to avoid memory cache
+ overhead for large I/O requests. It bypasses the data copy between application and kernel
+ memory, and avoids buffering the data in the client memory.</para>
</glossdef>
</glossentry>
<glossentry xml:id="dirstripdesc">
- <glossterm>Directory stripe descriptor
- </glossterm>
+ <glossterm>Directory stripe descriptor </glossterm>
+ <glossdef>
+ <para>An extended attribute that describes the default stripe pattern for new files created
+ within that directory. This is also inherited by new subdirectories at the time they are
+ created.</para>
+ </glossdef>
+ </glossentry>
+ <glossentry xml:id="DNE">
+ <glossterm>Distributed namespace (DNE)</glossterm>
<glossdef>
- <para>An extended attribute that describes the default stripe pattern for files underneath that directory.</para>
+ <para>A collection of metadata targets implementing a single file system namespace.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossterm>EA
</glossterm>
<glossdef>
- <para>Extended Attribute. A small amount of data which can be retrieved through a name associated with a particular inode. Lustre uses EAs to store striping information (location of file data on OSTs). Examples of extended attributes are ACLs, striping information, and crypto keys.</para>
+ <para>Extended attribute. A small amount of data that can be retrieved through a name (EA or
+ attr) associated with a particular inode. A Lustre file system uses EAs to store striping
+ information (indicating the location of file data on OSTs). Examples of extended
+ attributes are ACLs, striping information, and the FID of the file.</para>
</glossdef>
</glossentry>
<glossentry xml:id="eviction">
<glossterm>Eviction
</glossterm>
<glossdef>
- <para>The process of eliminating server state for a client that is not returning to the cluster after a timeout or if server failures have occurred.</para>
+ <para>The process of removing a client's state from the server if the client is unresponsive
+ to server requests after a timeout or if server recovery fails. If a client is still
+ running, it is required to flush the cache associated with the server when it becomes
+ aware that it has been evicted.</para>
</glossdef>
</glossentry>
<glossentry xml:id="export">
<para>The state held by a server for a client that is sufficient to transparently recover all in-flight operations when a single failure occurs.</para>
</glossdef>
</glossentry>
+ <glossentry>
+ <glossterm>Extent </glossterm>
+ <glossdef>
+ <para>A range of contiguous bytes or blocks in a file that are addressed by a {start,
+ length} tuple instead of individual block numbers.</para>
+ </glossdef>
+ </glossentry>
<glossentry xml:id="extendloc">
- <glossterm>Extent Lock
- </glossterm>
+ <glossterm>Extent lock </glossterm>
<glossdef>
- <para>A lock used by the OSC to protect an extent in a storage object for concurrent control of read/write, file size acquisition and truncation operations.</para>
+ <para>An LDLM lock used by the OSC to protect an extent in a storage object for concurrent
+ control of read/write, file size acquisition, and truncation operations.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossterm>Failback
</glossterm>
<glossdef>
- <para>The failover process in which the default active server regains control over the service.</para>
+ <para> The failover process in which the default active server regains control from the
+ backup server that had taken control of the service.</para>
</glossdef>
</glossentry>
<glossentry xml:id="failoutost">
<glossterm>Failout OST
</glossterm>
<glossdef>
- <para>An OST which is not expected to recover if it fails to answer client requests. A failout OST can be administratively failed, thereby enabling clients to return errors when accessing data on the failed OST without making additional network requests.</para>
+ <para>An OST that is not expected to recover if it fails to answer client requests. A
+ failout OST can be administratively failed, thereby enabling clients to return errors when
+ accessing data on the failed OST without making additional network requests or waiting for
+ OST recovery to complete.</para>
</glossdef>
</glossentry>
<glossentry xml:id="failover">
<glossterm>FID
</glossterm>
<glossdef>
- <para>Lustre File xml:identifier. A collection of integers which uniquely xml:identify a file or object. The FID structure contains a sequence, xml:identity and version number.</para>
+ <para> Lustre File Identifier. A 128-bit file system-unique identifier for a file or object
+ in the file system. The FID structure contains a unique 64-bit sequence number (see
+ <emphasis role="italic">FLDB</emphasis>), a 32-bit object ID (OID), and a 32-bit version
+ number. The sequence number is unique across all Lustre targets (OSTs and MDTs).</para>
</glossdef>
</glossentry>
<glossentry xml:id="fileset">
<glossterm>Fileset
</glossterm>
<glossdef>
- <para>A group of files that are defined through a directory that represents a file system's start point.</para>
+ <para>A group of files that are defined through a directory that represents the start point
+ of a file system.</para>
</glossdef>
</glossentry>
<glossentry xml:id="fldb">
<glossterm>FLDB
</glossterm>
<glossdef>
- <para>FID Location Database. This database maps a sequence of FIDs to a server which is managing the objects in the sequence.</para>
+ <para>FID location database. This database maps a sequence of FIDs to a specific target (MDT
+ or OST), which manages the objects within the sequence. The FLDB is cached by all clients
+ and servers in the file system, but is typically only modified when new servers are added
+ to the file system.</para>
</glossdef>
</glossentry>
<glossentry xml:id="flightgroup">
- <glossterm>Flight Group
- </glossterm>
+ <glossterm>Flight group </glossterm>
<glossdef>
- <para>Group or I/O transfer operations initiated in the OSC, which is simultaneously going between two endpoints. Tuning the flight group size correctly leads to a full pipe.</para>
+ <para>Group of I/O RPCs initiated by the OSC that are concurrently queued or processed at
+ the OST. Increasing the number of RPCs in flight for high latency networks can increase
+ throughput and reduce visible latency at the client.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>G</title>
<glossentry xml:id="glimpsecallback">
- <glossterm>Glimpse callback
- </glossterm>
- <glossdef>
- <para>An RPC made by an OST or MDT to another system (usually a client) to indicate a held extent lock should be surrendered. If the system is using the lock, then the system should report the object size in the reply to the glimpse callback. Glimpses are introduced to optimize the acquisition of file sizes.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="grouplock">
- <glossterm>Group Lock
- </glossterm>
+ <glossterm>Glimpse callback </glossterm>
<glossdef>
- <para> To follow.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="groupupcall">
- <glossterm>Group upcall
- </glossterm>
- <glossdef>
- <para> To follow.</para>
+ <para>An RPC made by an OST or MDT to another system (usually a client) to indicate that a
+ held extent lock should be surrendered. If the system is using the lock, then the system
+ should return the object size and timestamps in the reply to the glimpse callback instead
+ of cancelling the lock. Glimpses are introduced to optimize the acquisition of file
+ attributes without introducing contention on an active lock.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossterm>Import
</glossterm>
<glossdef>
- <para>The state held by a client to fully recover a transaction sequence after a server failure and restart.</para>
+ <para>The state held held by the client for each target that it is connected to. It holds
+ server NIDs, connection state, and uncommitted RPCs needed to fully recover a transaction
+ sequence after a server failure and restart.</para>
</glossdef>
</glossentry>
<glossentry xml:id="intentlock">
- <glossterm>Intent Lock
- </glossterm>
+ <glossterm>Intent lock </glossterm>
<glossdef>
- <para>A special locking operation introduced by Lustre into the Linux kernel. An intent lock combines a request for a lock, with the full information to perform the operation(s) for which the lock was requested. This offers the server the option of granting the lock or performing the operation and informing the client of the operation result without granting a lock. The use of intent locks enables metadata operations (even complicated ones), to be implemented with a single RPC from the client to the server.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="iov">
- <glossterm>IOV
- </glossterm>
- <glossdef>
- <para>I/O vector. A buffer destined for transport across the network which contains a collection (a/k/a as a vector) of blocks with data.</para>
- </glossdef>
- </glossentry>
- </glossdiv>
- <glossdiv>
- <title>K</title>
- <glossentry xml:id="kerberos">
- <glossterm>Kerberos
- </glossterm>
- <glossdef>
- <para>An authentication mechanism, optionally available in an upcoming Lustre version as a GSS backend.</para>
+ <para>A special Lustre file system locking operation in the Linux kernel. An intent lock
+ combines a request for a lock with the full information to perform the operation(s) for
+ which the lock was requested. This offers the server the option of granting the lock or
+ performing the operation and informing the client of the operation result without granting
+ a lock. The use of intent locks enables metadata operations (even complicated ones) to be
+ implemented with a single RPC from the client to the server.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossterm>LBUG
</glossterm>
<glossdef>
- <para>A bug that Lustre writes into a log indicating a serious system failure.</para>
+ <para>A fatal error condition detected by the software that halts execution of the kernel
+ thread to avoid potential further corruption of the system state. It is printed to the
+ console log and triggers a dump of the internal debug log. The system must be rebooted to
+ clear this state.</para>
</glossdef>
</glossentry>
<glossentry xml:id="ldlm">
<glossterm>lfs
</glossterm>
<glossdef>
- <para>The Lustre File System configuration tool for end users to set/check file striping, etc. See <link xl:href="UserUtilities.html#50438206_94597">glossdiv 32.1, lfs</link>.</para>
+ <para>The Lustre File System command-line utility that allows end users to interact with
+ Lustre-specific features, such as setting or checking file striping or per-target free
+ space. For more details, see <xref xmlns:xlink="http://www.w3.org/1999/xlink"
+ linkend="dbdoclet.50438206_94597"/>.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lfsck">
<glossterm>lfsck
</glossterm>
<glossdef>
- <para>Lustre File System Check. A distributed version of a disk file system checker. Normally, lfsck does not need to be run, except when file systems are damaged through multiple disk failures and other means that cannot be recovered using file system journal recovery.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="liblustre">
- <glossterm>liblustre
- </glossterm>
- <glossdef>
- <para>Lustre library. A user-mode Lustre client linked into a user program for Lustre fs access. liblustre clients cache no data, do not need to give back locks on time, and can recover safely from an eviction. They should not participate in recovery.</para>
+ <para>Lustre file system check. A distributed version of a disk file system checker.
+ Normally, <literal>lfsck</literal> does not need to be run, except when file systems are
+ damaged by events such as multiple disk failures and cannot be recovered using file system
+ journal recovery.</para>
</glossdef>
</glossentry>
<glossentry xml:id="llite">
- <glossterm>Llite
- </glossterm>
+ <glossterm>llite </glossterm>
<glossdef>
- <para>Lustre lite. This term is in use inside the code and module names to indicate that code elements are related to the Lustre file system.</para>
+ <para>Lustre lite. This term is in use inside code and in module names for code that is
+ related to the Linux client VFS interface.</para>
</glossdef>
</glossentry>
<glossentry xml:id="llog">
- <glossterm>Llog
- </glossterm>
+ <glossterm>llog </glossterm>
<glossdef>
- <para>Lustre log. A log of entries used internally by Lustre. An llog is suitable for rapid transactional appends of records and cheap cancellation of records through a bitmap.</para>
+ <para>Lustre log. An efficient log data structure used internally by the file system for
+ storing configuration and distributed transaction records. An <literal>llog</literal> is
+ suitable for rapid transactional appends of records and cheap cancellation of records
+ through a bitmap.</para>
</glossdef>
</glossentry>
<glossentry xml:id="llogcatalog">
- <glossterm>Llog Catalog
- </glossterm>
+ <glossterm>llog catalog </glossterm>
<glossdef>
- <para>Lustre log catalog. An llog with records that each point at an llog. Catalogs were introduced to give llogs almost infinite size. llogs have an originator which writes records and a replicator which cancels record (usually through an RPC), when the records are not needed.</para>
+ <para>Lustre log catalog. An <literal>llog</literal> with records that each point at an
+ <literal>llog</literal>. Catalogs were introduced to give <literal>llogs</literal>
+ increased scalability. <literal>llogs</literal> have an originator which writes records
+ and a replicator which cancels records when the records are no longer needed.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lmv">
<glossterm>LMV
</glossterm>
<glossdef>
- <para>Logical Metadata Volume. A driver to abstract in the Lustre client that it is working with a metadata cluster instead of a single metadata server.</para>
+ <para>Logical metadata volume. A module that implements a DNE client-side abstraction
+ device. It allows a client to work with many MDTs without changes to the llite module. The
+ LMV code forwards requests to the correct MDT based on name or directory striping
+ information and merges replies into a single result to pass back to the higher
+ <literal>llite</literal> layer that connects the Lustre file system with Linux VFS,
+ supports VFS semantics, and complies with POSIX interface specifications.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lnd">
<glossterm>LND
</glossterm>
<glossdef>
- <para>Lustre Network Driver. A code module that enables LNET support over a particular transport, such as TCP and various kinds of InfiniBand.</para>
+ <para>Lustre network driver. A code module that enables LNET support over particular
+ transports, such as TCP and various kinds of InfiniBand* networks.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lnet">
<para>Lustre Networking. A message passing network protocol capable of running and routing through various physical layers. LNET forms the underpinning of LNETrpc.</para>
</glossdef>
</glossentry>
- <glossentry xml:id="loadmds">
- <glossterm>Load-balancing MDSs
- </glossterm>
- <glossdef>
- <para>A cluster of MDSs that perform load balancing of on system requests.</para>
- </glossdef>
- </glossentry>
<glossentry xml:id="lockclient">
- <glossterm>Lock Client
- </glossterm>
+ <glossterm>Lock client </glossterm>
<glossdef>
- <para>A module that makes lock RPCs to a lock server and handles revocations from the server.</para>
+ <para>A module that makes lock RPCs to a lock server and handles revocations from the
+ server.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lockserver">
- <glossterm>Lock Server
- </glossterm>
+ <glossterm>Lock server </glossterm>
<glossdef>
- <para>A system that manages locks on certain objects. It also issues lock callback requests, calls while servicing or, for objects that are already locked, completes lock requests.</para>
+ <para>A service that is co-located with a storage target that manages locks on certain
+ objects. It also issues lock callback requests, calls while servicing or, for objects that
+ are already locked, completes lock requests.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lov">
<glossterm>LOV
</glossterm>
<glossdef>
- <para>Logical Object Volume. The object storage analog of a logical volume in a block device volume management system, such as LVM or EVMS. The LOV is primarily used to present a collection of OSTs as a single device to the MDT and client file system drivers.</para>
+ <para>Logical object volume. The object storage analog of a logical volume in a block device
+ volume management system, such as LVM or EVMS. The LOV is primarily used to present a
+ collection of OSTs as a single device to the MDT and client file system drivers.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lovdes">
<glossterm>LOV descriptor
</glossterm>
<glossdef>
- <para>A set of configuration directives which describes which nodes are OSS systems in the Lustre cluster, providing names for their OSTs.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="lustre">
- <glossterm>Lustre
- </glossterm>
- <glossdef>
- <para>The name of the project chosen by Peter Braam in 1999 for an object-based storage architecture. Now the name is commonly associated with the Lustre file system.</para>
+ <para>A set of configuration directives which describes which nodes are OSS systems in the
+ Lustre cluster and providing names for their OSTs.</para>
</glossdef>
</glossentry>
<glossentry xml:id="lustreclient">
<glossterm>Lustre file
</glossterm>
<glossdef>
- <para>A file in the Lustre file system. The implementation of a Lustre file is through an inode on a metadata server which contains references to a storage object on OSSs.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="lustrelite">
- <glossterm>Lustre lite
- </glossterm>
- <glossdef>
- <para>A preliminary version of Lustre developed for LLNL in 2002. With the release of Lustre 1.0 in late 2003, Lustre Lite became obsolete.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="lvfs">
- <glossterm>Lvfs
- </glossterm>
- <glossdef>
- <para>A library that provides an interface between Lustre OSD and MDD drivers and file systems; this avoids introducing file system-specific abstractions into the OSD and MDD drivers.</para>
+ <para>A file in the Lustre file system. The implementation of a Lustre file is through an
+ inode on a metadata server that contains references to a storage object on OSSs.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>M</title>
<glossentry xml:id="mballoc">
- <glossterm>Mballoc
- </glossterm>
+ <glossterm>mballoc </glossterm>
<glossdef>
- <para>Multi-Block-Allocate. Lustre functionality that enables the ldiskfs file system to allocate multiple blocks with a single request to the block allocator. Normally, an ldiskfs file system only allocates only one block per request.</para>
+ <para>Multi-block allocate. Functionality in ext4 that enables the
+ <literal>ldiskfs</literal> file system to allocate multiple blocks with a single request
+ to the block allocator. </para>
</glossdef>
</glossentry>
<glossentry xml:id="mdc">
<glossterm>MDC
</glossterm>
<glossdef>
- <para>MetaData Client - Lustre client component that sends metadata requests via RPC over LNET to the Metadata Target (MDT).</para>
+ <para>Metadata client. A Lustre client component that sends metadata requests via RPC over
+ LNET to the metadata target (MDT).</para>
</glossdef>
</glossentry>
<glossentry xml:id="mdd">
<glossterm>MDD
</glossterm>
<glossdef>
- <para>MetaData Disk Device - Lustre server component that interfaces with the underlying Object Storage Device to manage the Lustre file system namespace (directories, file ownership, attributes).</para>
+ <para>Metadata disk device. Lustre server component that interfaces with the underlying
+ object storage device to manage the Lustre file system namespace (directories, file
+ ownership, attributes).</para>
</glossdef>
</glossentry>
<glossentry xml:id="mds">
<glossterm>MDS
</glossterm>
<glossdef>
- <para>MetaData Server - Server node that is hosting the Metadata Target (MDT).</para>
+ <para>Metadata server. The server node that is hosting the metadata target (MDT).</para>
</glossdef>
</glossentry>
<glossentry xml:id="mdt">
<glossterm>MDT
</glossterm>
<glossdef>
- <para>Metadata Target. A metadata device made available through the Lustre meta-data network protocol.</para>
+ <para>Metadata target. A storage device containing the file system namespace that is made
+ available over the network to a client. It stores filenames, attributes, and the layout of
+ OST objects that store the file data.</para>
</glossdef>
</glossentry>
<glossentry xml:id="mdt0" condition='l24'>
<glossterm>MDT0
</glossterm>
<glossdef>
- <para>The metadata target for the file system root. Since Lustre 2.4, multiple metadata targets are possible in the same filesystem. MDT0 is the root of the filesystem which must be available for the filesystem to be accessible.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="metadatawriteback">
- <glossterm>Metadata Write-back Cache
- </glossterm>
- <glossdef>
- <para>A cache of metadata updates (mkdir, create, setattr, other operations) which an application has performed, but have not yet been flushed to a storage device or server.</para>
+ <para>The metadata target for the file system root. Since Lustre release 2.4, multiple
+ metadata targets are possible in the same file system. MDT0 is the root of the file
+ system, which must be available for the file system to be accessible.</para>
</glossdef>
</glossentry>
<glossentry xml:id="mgs">
<glossterm>MGS
</glossterm>
<glossdef>
- <para>Management Service. A software module that manages the startup configuration and changes to the configuration. Also, the server node on which this system runs.</para>
+ <para>Management service. A software module that manages the startup configuration and
+ changes to the configuration. Also, the server node on which this system runs.</para>
</glossdef>
</glossentry>
<glossentry xml:id="mountconf">
- <glossterm>Mountconf
- </glossterm>
+ <glossterm>mountconf </glossterm>
<glossdef>
- <para>The Lustre configuration protocol that formats disk file systems on servers with the mkfs.lustre program, and prepares them for automatic incorporation into a Lustre cluster. This allows clients to be configured and mounted with a simple <literal>mount</literal> command.</para>
+ <para>The Lustre configuration protocol that formats disk file systems on servers with the
+ <literal>mkfs.lustre</literal> program, and prepares them for automatic incorporation
+ into a Lustre cluster. This allows clients to be configured and mounted with a simple
+ <literal>mount</literal> command.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>N</title>
- <glossentry xml:id="nal">
- <glossterm>NAL
- </glossterm>
- <glossdef>
- <para>An older, obsolete term for LND.</para>
- </glossdef>
- </glossentry>
<glossentry xml:id="nid">
<glossterm>NID
</glossterm>
<glossdef>
- <para>Network xml:identifier. Encodes the type, network number and network address of a network interface on a node for use by Lustre.</para>
+ <para>Network identifier. Encodes the type, network number, and network address of a network
+ interface on a node for use by the Lustre file system.</para>
</glossdef>
</glossentry>
<glossentry xml:id="nioapi">
</glossdef>
</glossentry>
<glossentry xml:id="nodeaffdef">
- <glossterm>Node Affinity
- </glossterm>
+ <glossterm>Node affinity </glossterm>
<glossdef>
- <para>Node Affinity describes the property of a multithreaded application to behave sensibably on multiple cores. Without the property of Node Affinity, an operating scheduler may move application threads accross processors in an sub-optimal way that significantly reduces performance of the application overall.</para>
+ <para>Node affinity describes the property of a multi-threaded application to behave
+ sensibly on multiple cores. Without the property of node affinity, an operating scheduler
+ may move application threads across processors in a sub-optimal way that significantly
+ reduces performance of the application overall.</para>
</glossdef>
</glossentry>
<glossentry xml:id="nrs">
<glossterm>NRS
</glossterm>
<glossdef>
- <para>Network Request Scheduler. A subcomponent of the PTLRPC layer, which determines the order in which RPCs are handled at servers.</para>
+ <para>Network request scheduler. A subcomponent of the PTLRPC layer, which specifies the
+ order in which RPCs are handled at servers. This allows optimizing large numbers of
+ incoming requests for disk access patterns, fairness between clients, and other
+ administrator-selected policies.</para>
</glossdef>
</glossentry>
<glossentry xml:id="NUMAdef">
<glossterm>NUMA
</glossterm>
<glossdef>
- <para>Non-Uniform Memory Access describes a mulitprocessing architecture where the time taken to access given memory differs depending on memory location releative to a given processor. Typically machines with multiple sockets are NUMA architectures.</para>
+ <para>Non-uniform memory access. Describes a multi-processing architecture where the time
+ taken to access given memory differs depending on memory location relative to a given
+ processor. Typically machines with multiple sockets are NUMA architectures.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>O</title>
<glossentry xml:id="odb">
- <glossterm>OBD
- </glossterm>
+ <glossterm>OBD </glossterm>
<glossdef>
- <para>Object Device. The base class of layering software constructs that provides Lustre functionality.</para>
+ <para>Object-based device. The generic term for components in the Lustre software stack that
+ can be configured on the client or server. Examples include MDC, OSC, LOV, MDT, and
+ OST.</para>
</glossdef>
</glossentry>
<glossentry xml:id="odbapi">
- <glossterm>OBD API
- </glossterm>
+ <glossterm>OBD API </glossterm>
<glossdef>
- <para>See Storage Object API.</para>
+ <para>The programming interface for configuring OBD devices. This was formerly also the API
+ for accessing object IO and attribute methods on both the client and server, but has been
+ replaced by the OSD API in most parts of the code.</para>
</glossdef>
</glossentry>
<glossentry xml:id="odbtype">
- <glossterm>OBD type
- </glossterm>
+ <glossterm>OBD type </glossterm>
<glossdef>
- <para>Module that can implement the Lustre object or metadata APIs. Examples of OBD types include the LOV, OSC and OSD.</para>
+ <para>Module that can implement the Lustre object or metadata APIs. Examples of OBD types
+ include the LOV, OSC and OSD.</para>
</glossdef>
</glossentry>
<glossentry xml:id="odbfilter">
- <glossterm>Obdfilter
- </glossterm>
- <glossdef>
- <para>An older name for the OSD device driver.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="objectdev">
- <glossterm>Object device
- </glossterm>
+ <glossterm>Obdfilter </glossterm>
<glossdef>
- <para>An instance of an object that exports the OBD API.</para>
+ <para>An older name for the OBD API data object operation device driver that sits between
+ the OST and the OSD. In Lustre 2.4 this device has been renamed OFD."</para>
</glossdef>
</glossentry>
<glossentry xml:id="objectstorage">
- <glossterm>Object storage
- </glossterm>
+ <glossterm>Object storage </glossterm>
<glossdef>
- <para>Refers to a storage-device API or protocol involving storage objects. The two most well known instances of object storage are the T10 iSCSI storage object protocol and the Lustre object storage protocol (a network implementation of the Lustre object API). The principal difference between the Lustre and T10 protocols is that Lustre includes locking and recovery control in the protocol and is not tied to a SCSI transport layer.</para>
+ <para>Refers to a storage-device API or protocol involving storage objects. The two most
+ well known instances of object storage are the T10 iSCSI storage object protocol and the
+ Lustre object storage protocol (a network implementation of the Lustre object API). The
+ principal difference between the Lustre and T10 protocols is that the Lustre protocol
+ includes locking and recovery control in the protocol and is not tied to a SCSI transport
+ layer.</para>
</glossdef>
</glossentry>
<glossentry xml:id="opencache">
- <glossterm>opencache
- </glossterm>
+ <glossterm>opencache </glossterm>
<glossdef>
<para>A cache of open file handles. This is a performance enhancement for NFS.</para>
</glossdef>
</glossentry>
<glossentry xml:id="orphanobjects">
- <glossterm>Orphan objects
- </glossterm>
- <glossdef>
- <para>Storage objects for which there is no Lustre file pointing at them. Orphan objects can arise from crashes and are automatically removed by an llog recovery. When a client deletes a file, the MDT gives back a cookie for each stripe. The client then sends the cookie and directs the OST to delete the stripe. Finally, the OST sends the cookie back to the MDT to cancel it.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="orphanhandling">
- <glossterm>Orphan handling
- </glossterm>
+ <glossterm>Orphan objects </glossterm>
<glossdef>
- <para>A component of the metadata service which allows for recovery of open, unlinked files after a server crash. The implementation of this feature retains open, unlinked files as orphan objects until it is determined that no clients are using them.</para>
+ <para>Storage objects to which no Lustre file points. Orphan objects can arise from crashes
+ and are automatically removed by an <literal>llog</literal> recovery between the MDT and
+ OST. When a client deletes a file, the MDT unlinks it from the namespace. If this is the
+ last link, it will atomically add the OST objects into a per-OST <literal>llog</literal>
+ (if a crash has occurred) and then wait until the unlink commits to disk. (At this point,
+ it is safe to destroy the OST objects. Once the destroy is committed, the MDT
+ <literal>llog</literal> records can be cancelled.)</para>
</glossdef>
</glossentry>
<glossentry xml:id="osc">
- <glossterm>OSC
- </glossterm>
+ <glossterm>OSC </glossterm>
<glossdef>
- <para>Object Storage Client. The client unit talking to an OST (via an OSS).</para>
+ <para>Object storage client. The client module communicating to an OST (via an OSS).</para>
</glossdef>
</glossentry>
<glossentry xml:id="osd">
- <glossterm>OSD
- </glossterm>
+ <glossterm>OSD </glossterm>
<glossdef>
- <para>Object Storage Device. A generic, industry term for storage devices with more extended interface than block-oriented devices, such as disks. Lustre uses this name to describe to a software module that implements an object storage API in the kernel. Lustre also uses this name to refer to an instance of an object storage device created by that driver. The OSD device is layered on a file system, with methods that mimic create, destroy and I/O operations on file inodes.</para>
+ <para>Object storage device. A generic, industry term for storage devices with a more
+ extended interface than block-oriented devices such as disks. For the Lustre file system,
+ this name is used to describe a software module that implements an object storage API in
+ the kernel. It is also used to refer to an instance of an object storage device created by
+ that driver. The OSD device is layered on a file system, with methods that mimic create,
+ destroy and I/O operations on file inodes.</para>
</glossdef>
</glossentry>
<glossentry xml:id="oss">
- <glossterm>OSS
- </glossterm>
+ <glossterm>OSS </glossterm>
<glossdef>
- <para>Object Storage Server. A server OBD that provides access to local OSTs.</para>
+ <para>Object storage server. A server OBD that provides access to local OSTs.</para>
</glossdef>
</glossentry>
<glossentry xml:id="ost">
- <glossterm>OST
- </glossterm>
+ <glossterm>OST </glossterm>
<glossdef>
- <para>Object Storage Target. An OSD made accessible through a network protocol. Typically, an OST is associated with a unique OSD which, in turn is associated with a formatted disk file system on the server containing the storage objects.</para>
+ <para>Object storage target. An OSD made accessible through a network protocol. Typically,
+ an OST is associated with a unique OSD which, in turn is associated with a formatted disk
+ file system on the server containing the data objects.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>P</title>
<glossentry xml:id="pdirops">
- <glossterm>Pdirops
- </glossterm>
+ <glossterm>pdirops </glossterm>
<glossdef>
- <para>A locking protocol introduced in the VFS by CFS to allow for concurrent operations on a single directory inode.</para>
+ <para>A locking protocol in the Linux VFS layer that allows for directory operations
+ performed in parallel.</para>
</glossdef>
</glossentry>
<glossentry xml:id="pool">
- <glossterm>pool
- </glossterm>
+ <glossterm>Pool </glossterm>
<glossdef>
- <para>OST pools allows the administrator to associate a name with an arbitrary subset of OSTs in a Lustre cluster. A group of OSTs can be combined into a named pool with unique access permissions and stripe characteristics.</para>
+ <para>OST pools allows the administrator to associate a name with an arbitrary subset of
+ OSTs in a Lustre cluster. A group of OSTs can be combined into a named pool with unique
+ access permissions and stripe characteristics.</para>
</glossdef>
</glossentry>
<glossentry xml:id="portal">
- <glossterm>Portal
- </glossterm>
+ <glossterm>Portal </glossterm>
<glossdef>
- <para>A concept used by LNET. LNET messages are sent to a portal on a NID. Portals can receive packets when a memory descriptor is attached to the portal. Portals are implemented as integers.</para>
- <para>Examples of portals are the portals on which certain groups of object, metadata, configuration and locking requests and replies are received.</para>
+ <para>A service address on an LNET NID that binds requests to a specific request service,
+ such as an MDS, MGS, OSS, or LDLM. Services may listen on multiple portals to ensure that
+ high priority messages are not queued behind many slow requests on another portal.</para>
</glossdef>
</glossentry>
<glossentry xml:id="ptlrpc">
</glossdef>
</glossentry>
<glossentry xml:id="replay">
- <glossterm>Reply
- </glossterm>
+ <glossterm>Replay request</glossterm>
<glossdef>
- <para>The concept of re-executing a server request after the server lost information in its memory caches and shut down. The replay requests are retained by clients until the server(s) have confirmed that the data is persistent on disk. Only requests for which a client has received a reply are replayed.</para>
+ <para>The concept of re-executing a server request after the server has lost information in
+ its memory caches and shut down. The replay requests are retained by clients until the
+ server(s) have confirmed that the data is persistent on disk. Only requests for which a
+ client received a reply and were assigned a transaction number by the server are replayed.
+ Requests that did not get a reply are resent.</para>
</glossdef>
</glossentry>
<glossentry xml:id="resent">
- <glossterm>Re-sent request
- </glossterm>
+ <glossterm>Resent request </glossterm>
<glossdef>
- <para>A request that has seen no reply can be re-sent after a server reboot.</para>
+ <para>An RPC request sent from a client to a server that has not had a reply from the
+ server. This might happen if the request was lost on the way to the server, if the reply
+ was lost on the way back from the server, or if the server crashes before or after
+ processing the request. During server RPC recovery processing, resent requests are
+ processed after replayed requests, and use the client RPC XID to determine if the resent
+ RPC request was already executed on the server. </para>
</glossdef>
</glossentry>
<glossentry xml:id="revocation">
- <glossterm>Revocation Callback
- </glossterm>
- <glossdef>
- <para>An RPC made by an OST or MDT to another system, usually a client, to revoke a granted lock.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="rollback">
- <glossterm>Rollback
- </glossterm>
+ <glossterm>Revocation callback </glossterm>
<glossdef>
- <para>The concept that server state is in a crash lost because it was cached in memory and not yet persistent on disk.</para>
+ <para>Also called a "blocking callback". An RPC request made by the lock server (typically
+ for an OST or MDT) to a lock client to revoke a granted DLM lock.</para>
</glossdef>
</glossentry>
<glossentry xml:id="rootsquash">
<glossterm>Root squash
</glossterm>
<glossdef>
- <para>A mechanism whereby the xml:identity of a root user on a client system is mapped to a different xml:identity on the server to avoid root users on clients gaining broad permissions on servers. Typically, for management purposes, at least one client system should not be subject to root squash.</para>
+ <para>A mechanism whereby the identity of a root user on a client system is mapped to a
+ different identity on the server to avoid root users on clients from accessing or
+ modifying root-owned files on the servers. This does not prevent root users on the client
+ from assuming the identity of a non-root user, so should not be considered a robust
+ security mechanism. Typically, for management purposes, at least one client system should
+ not be subject to root squash.</para>
</glossdef>
</glossentry>
<glossentry xml:id="routing">
- <glossterm>routing
- </glossterm>
+ <glossterm>Routing </glossterm>
<glossdef>
<para>LNET routing between different networks and LNDs.</para>
</glossdef>
<glossterm>RPC
</glossterm>
<glossdef>
- <para>Remote Procedure Call. A network encoding of a request.</para>
+ <para>Remote procedure call. A network encoding of a request.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossdiv>
<title>S</title>
- <glossentry xml:id="storageobjapi">
- <glossterm>Storage Object API
- </glossterm>
- <glossdef>
- <para>The API that manipulates storage objects. This API is richer than that of block devices and includes the create/delete of storage objects, read/write of buffers from and to certain offsets, set attributes and other storage object metadata.</para>
- </glossdef>
- </glossentry>
- <glossentry xml:id="storageobjects">
- <glossterm>Storage Objects
- </glossterm>
- <glossdef>
- <para>A generic concept referring to data containers, similar/identical to file inodes.</para>
- </glossdef>
- </glossentry>
<glossentry xml:id="stride">
- <glossterm>Stride
- </glossterm>
+ <glossterm>Stripe </glossterm>
<glossdef>
- <para>A contiguous, logical extent of a Lustre file written to a single OST.</para>
+ <para>A contiguous, logical extent of a Lustre file written to a single OST. Used
+ synonymously with a single OST data object that makes up part of a file visible to user
+ applications.</para>
</glossdef>
</glossentry>
<glossentry xml:id="stridesize">
- <glossterm>Stride size
- </glossterm>
+ <glossterm>Stripe size </glossterm>
<glossdef>
- <para>The maximum size of a stride, typically 4 MB.</para>
+ <para>The maximum number of bytes that will be written to an OST object before the next
+ object in a file's layout is used when writing sequential data to a file. Once a full
+ stripe has been written to each of the objects in the layout, the first object will be
+ written to again in round-robin fashion.</para>
</glossdef>
</glossentry>
<glossentry xml:id="stripcount">
<glossterm>Striping metadata
</glossterm>
<glossdef>
- <para>The extended attribute associated with a file that describes how its data is distributed over storage objects. See also default stripe pattern.</para>
+ <para>The extended attribute associated with a file that describes how its data is
+ distributed over storage objects. See also <emphasis role="italic">Default stripe
+ pattern</emphasis>.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossterm>T10 object protocol
</glossterm>
<glossdef>
- <para>An object storage protocol tied to the SCSI transport layer. Lustre does not use T10.</para>
+ <para>An object storage protocol tied to the SCSI transport layer. The Lustre file system
+ does not use T10.</para>
</glossdef>
</glossentry>
</glossdiv>
<glossterm>Wide striping
</glossterm>
<glossdef>
- <para>Strategy of using many OSTs to store stripes of a single file. This obtains maximum bandwidth to a single file through parallel utilization of many OSTs.</para>
+ <para>Strategy of using many OSTs to store stripes of a single file. This obtains maximum
+ bandwidth access to a single file through parallel utilization of many OSTs.</para>
</glossdef>
</glossentry>
</glossdiv>
git://git.whamcloud.com / doc / manual.git / commitdiff