[LU-15494] DNE3: "lfs setdirstripe -D" for specific MDTs

• Status: Open
• Project: Lustre
• Type: New Feature
• Priority: Major
• Reporter: Andreas Dilger
• Assignee: WC Triage
• Resolution: Unresolved
• Labels: dne3

Description

Request to enhance the functionality of "lfs setdirstripe" to allow the selection of specific MDTs in the default layout as opposed to only the starting MDT and count.

The current implementation allows for stripe on a specific series of MDTs, e.g.:

# lfs mkdir [-c 4] -i 1,2,4,6  /some/dir

but not to set this as the default layout on a parent directory:

# lfs setdirstripe -D [-c 4] -i 1,2,4,6 /some/dir
lfs setdirstripe: cannot create stripe dir '/some/dir': Invalid argument

This should stripe subdirectories of /some/dir across 4 MDTs with the specified indexes.

Currently, the --stripe_count|-c and number of specified MDT indices need to match (the -c argument is implicitly set to the number of MDTs specified if not given).

It would be useful to allow specifying a subset of MDTs for allocation in some cases, either to keep a directory tree on a small subset of MDTs for admin/performance/locality reasons, or during migration to avoid striping a whole tree across all of the specified MDTs, while avoiding over-full MDTs:

lfs setdirstripe -D -c1 -i 1,3,5,7 /some/dir

This should stripe to only one of 4 specified MDTs with the indexes 1, 3, 5 & 7

This will allow for more controllable striping in a case where a file system could have many MDTs across many systems, and in cases where multiple MDTs may exist on one server, or some clients may be closer to specific MDTs than others.

Issue Links

• Clones: LU-8616 DNE3: enhance "lfs mkdir" to select s...
• is related to: LU-11571 MDT pool
• is related to: LU-9392 lfs migrate -o and lfs setstripe -o s...
• is related to: LU-10766 Incorrect freeing in llapi_dir_create
• is related to: LU-7827 DNE3: automatically select MDT for lf...