X-Git-Url: https://git.whamcloud.com/?a=blobdiff_plain;f=UnderstandingFailover.xml;h=7ff66d3482e46609e9ba5f7f2ef69a6d56d15472;hb=e096f06b81ed50da7c6f21867162f272299465ef;hp=ef215cc42d9295d2b82a5a58a5a0aa3f3a520670;hpb=bfc3782667e73a23f28a7b9cac0df416e9b575b0;p=doc%2Fmanual.git diff --git a/UnderstandingFailover.xml b/UnderstandingFailover.xml index ef215cc..7ff66d3 100644 --- a/UnderstandingFailover.xml +++ b/UnderstandingFailover.xml @@ -1,7 +1,7 @@ + xmlns:xl="http://www.w3.org/1999/xlink" version="5.0" xml:lang="en-US" + xml:id="understandingfailover"> Understanding Failover in a Lustre File System This chapter describes failover in a Lustre file system. It @@ -105,28 +105,26 @@ xml:id="understandingfailover"> - Active/passivepair - In this + Active/passive pair - In this configuration, the active node provides resources and serves data, while the passive node is usually standing by idle. If the active node fails, the passive node takes over and becomes active. - Active/activepair - In this + Active/active pair - In this configuration, both nodes are active, each providing a subset of resources. In case of a failure, the second node takes over resources from the failed node. - In Lustre software releases previous to Lustre software release - 2.4, MDSs can be configured as an active/passive pair, while OSSs can be - deployed in an active/active configuration that provides redundancy + If there is a single MDT in a filesystem, two MDSes can be + configured as an active/passive pair, while pairs of OSSes can be + deployed in an active/active configuration that improves OST availability without extra overhead. Often the standby MDS is the active MDS for another Lustre file system or the MGS, so no nodes are idle in the - cluster. - Lustre software release 2.4 introduces metadata - targets for individual sub-directories. Active-active failover - configurations are available for MDSs that serve MDTs on shared + cluster. If there are multiple MDTs in a filesystem, active-active + failover configurations are available for MDSs that serve MDTs on shared storage. @@ -149,11 +147,10 @@ xml:id="understandingfailover"> For MDT failover, two MDSs can be configured to serve the same - MDT. Only one MDS node can serve an MDT at a time. - Lustresoftware release 2.4 allows multiple MDTs. - By placing two or more MDT partitions on storage shared by two MDSs, - one MDS can fail and the remaining MDS can begin serving the unserved - MDT. This is described as an active/active failover pair. + MDT. Only one MDS node can serve any MDT at one time. + By placing two or more MDT devices on storage shared by two MDSs, + one MDS can fail and the remaining MDS can begin serving the unserved + MDT. This is described as an active/active failover pair. For OST failover, multiple OSS nodes can be configured to be able @@ -170,8 +167,8 @@ xml:id="understandingfailover"> active (using tunefs.lustre). For explanations of these utilities, see - and - . + and + . Failover capability in a Lustre file system can be used to upgrade the Lustre software between successive minor versions without cluster downtime. For more information, see @@ -210,9 +207,8 @@ xml:id="understandingfailover"> configured in a quasi active/active configuration, with each MDS managing metadata for a subset of the Lustre file system. -
- Lustre failover - configuration for a active/passive MDT +
+ Lustre failover configuration for a active/passive MDT @@ -223,19 +219,17 @@ xml:id="understandingfailover">
-
+
<indexterm> <primary>failover</primary> <secondary>MDT</secondary> </indexterm>MDT Failover Configuration (Active/Active) - Multiple MDTs became available with the advent of Lustre software - release 2.4. MDTs can be setup as an active/active failover + MDTs can be configured as an active/active failover configuration. A failover cluster is built from two MDSs as shown in . -
- Lustre failover - configuration for a active/active MDTs +
+ Lustre failover configuration for a active/active MDTs OSSs configured as a failover pair must have shared disks/RAID. -
- Lustre failover - configuration for an OSTs +
+ Lustre failover configuration for an OSTs
+