lfs migrate \- migrate files or directories between MDTs or OSTs.
.SH SYNOPSIS
.B lfs migrate
-\fI-m mdt_idx\fR [-v|--verbose] \fI<directory>\fR
+.RI [ SETSTRIPE_OPTIONS " ... ] <" file "> ..."
.br
-.B lfs migrate
-.RI [OPTIONS] ... <file|directory>\fR...
+.B lfs migrate -m mdt_idx
+.RB [ -v | --verbose ]
+.RI < directory >
.br
.SH DESCRIPTION
-Migrate MDT inodes or OST objects between MDTs and OSTs respectively. For the
-case of MDT inode migration:
+Migrate OST objects or MDT inodes between MDTs and OSTs respectively.
+.P
+The
+.B lfs migrate
+command can be used for moving files from one (or more) OSTs to other
+OSTs (e.g. for space balancing between OSTs, or to evacuate an OST for
+hardware reasons), to change the stripe count or other layout parameters
+of a file (e.g. to increase the bandwidth of a file by striping it over
+multiple OSTs), or to move the file between different classes of storage
+(e.g. SSD vs. HDD OSTs, or local vs. remote OSTs in different pools).
+.P
+In OST object migration mode, the command supports the same
+.I SETSTRIPE_OPTIONS
+listed in
+.BR lfs-setstripe (1)
+to specify the layout of the target file. The migrate command differs
+from
+.B lfs setstripe
+in that
+.B lfs migrate
+will copy the data from the existing file(s) using the new layout parameters
+to the new OST(s). In contrast,
+.B lfs setstripe
+is used for creating new (empty) files with the specified layout.
+.SH OST MIGRATE OPTIONS
+For OST object migration, there additional options available:
.TP
-.B migrate -m|--mdt-index <mdt_idx> \fIdirectory\fR
-.br
-Move the file metadata (inode) from one MDT to MDT with index \fBmdt_idx\fR.
+.BR -b , --block
+Block access to the file by other applications during data migration
+(default). This prevents other processes from accessing the file during
+migration, which prevents data data writes to the old file objects from
+being lost. This should be used if an OST needs to be completely emptied
+prior to its removal, to ensure all requested files are migrated off the
+OST.
+.TP
+.BR -n , --non-block
+Abort migration if concurrent file access is detected. This can be
+used with OST space balancing migration to avoid interfering with file
+access by applications if there is not a requirement to migrate any
+particular file to the new layout.
+.TP
+.BR -D , --non-direct
+Do
+.B not
+use
+.B O_DIRECT
+read and write operations when migrating a file. The
+.B O_DIRECT
+option avoids data copy from kernel buffers into userspace, which can
+impose CPU and memory overhead on the copy operation, but makes read and
+write operations synchronous. Using the
+.B --non-direct
+option uses buffered read/write operations, which may improve migration
+speed at the cost of more CPU and memory overhead.
+.P
+NOTE:
+.B lfs migrate
+has a complementary
+.B lfs_migrate
+script which is used to provide extra functionality when migrating file
+data between OSTs and has a separate man page. See
+.BR lfs_migrate (1)
+for details.
+.SH MDT MIGRATE OPTIONS
+.TP
+.RB -m , --mdt-index
+Causes the file metadata (inode) to be migrated to the MDT with index
+.IR mdt_idx .
+This is useful if new MDTs have been added to a filesystem and existing
+user or project directories should be migrated off old MDTs to balance
+the space usage and future metadata workload.
+.P
Migration of striped directories or individual files between MDTs is not
currently supported. Only the root user can migrate directories. Files that
have been archived by HSM or are currently open are skipped by MDT inode
complete.
.TP
\fIWARNING\fR
-A migrated file or directory will have a new inode number and FID. As
-a consequence, files archieved by Lustre HSM cannot currently be migrated
-and migrated files that have a new inode number may confuse backup tools.
-.TP
-For the case of OST object migration:
-.TP
-.B migrate
-.B [--stripe-count|-c \fIstripe_count\fR]
-.B [--stripe-index|-i \fIstart_ost_idx\fR]
-.B [--stripe-size|-S \fIstripe_size\fR]
-.B [--pool|-p \fIpool_name\fR]
-.B [--ost-list|-o \fIost_indices\fR]
-.B [--component-end|-E \fIcomp_end\fR]
-.B [--block|-b]
-.B [--non-block|-n]
-.B [--non-direct|-D] \fIfile|directory\fR
-.br
-Migrate can also be used for OST objects by omitting \fI-m\fR option. In this
-mode, the command has identical options to
-.BR lfs-setstripe (1).
-The difference between migrate and setstripe is that \fImigrate\fR will
-re-layout the data in existing files using the new layout parameter by copying
-the data from the existing OST(s) to the new OST(s). In contrast,
-\fIsetstripe\fR is used for creating new files with the specified layout. For
-more information, see lfs-setstripe(1).
-.P
-NOTE: lfs migrate has a complementary script
-.B lfs_migrate
-which is used to provide extra functionality when migrating file data
-between OSTs and has a separate man page.
+A migrated file or directory will have a new FID, and hence a new inode
+number. As a consequence, files archived by Lustre HSM that depend on
+the FID as the identifier in the HSM archive cannot currently be migrated.
+Having a new inode number may also cause backup tools to consider the
+migrated file(s) to be a new, and cause them to be backed up again.
.SH EXAMPLES
.TP
-.B $ lfs migrate -m 0 ./testremote
-Move the inodes contained in ./testremote from their current MDT to the
-MDT with index 0.
-.TP
.B $ lfs migrate -c 2 /mnt/lustre/file1
-This migrate the file into a new layout with 2 stripes.
+This migrates the file into a new layout with 2 stripes.
.TP
.B $ lfs migrate -E 64M -c 1 -E 256M -c 4 -E -1 -c -1 /mnt/lustre/file1
-This migrate the file into a three components composite layout.
+This migrates the file into a three component composite layout.
+.TP
+.B $ lfs migrate -m 0 ./testremote
+Move the inodes contained in directory ./testremote from their current
+MDT to the MDT with index 0.
.SH AUTHOR
The lfs command is part of the Lustre filesystem.
.SH SEE ALSO
git://git.whamcloud.com / fs / lustre-release.git / blobdiff