[LU-15307] Option to set max directory stripe count per filesystem

• Type: New Feature
• Resolution: Fixed
• Priority: Critical
• Fix Version/s: Lustre 2.15.0
• Affects Version/s: Lustre 2.7.0
• Labels: easy
• Assignee: Feng Lei
• Reporter: Andreas Dilger

Description

We have users that will set directory stripe count by using "-1" as in
"lfs setdirstripe -c -1".

Filesystem with small number of MDTs (4-8) this was ok. But as the MDT count gets lager (>32) this is not always desirable. Most of the time we don't want users to set directory stripe counts so large. We would like config option for max default directory size setting for ("lfs setdirstripe -c -1"). But would still like the ability to allow setting stripe counts larger for those who explicitly request it, but not unintentionally.

Issue Links

• Clones: LU-9162 Option to set max stripe count per filesystem
• is related to: LU-15314 set default max-inherit to 3 for default dir stripe policy if stripe count is not 0 or 1
• is related to: LUDOC-501 Document (dir)stripe limits
• is related to: LU-10329 DNE3: REMOTE_PARENT_DIR scalability

Comments

[Peter Jones]

Landed for 2.15

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/45724/
Subject: LU-15307 lod: add option to set max dir stripe count
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 09c83ef26cca5b27bfbc05538c2df93d5a396fb7

[Gerrit Updater]

"Feng, Lei <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/45724
Subject: LU-15307 lod: add option to set max dir stripe count
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 5aa4307f3d5d058f09f1636180b541c870b44031

[Feng Lei]

Split the requirement of lfs setdirstripe command to LU-15314

[Andreas Dilger]

In addition to limiting the stripe count used when selecting "-c -1" it also makes sense to return an error from "lfs setdirstripe" when creating a default directory striping that has a stripe count > 1 but does not have max-inherit set. There have repeatedly been problems hit when a filesystem is configured with "lfs setdirstripe -c N -D $MOUNT" (for any N > 1) causing REMOTE_PARENT_DIR to be filled or have tens of millions of entries, excessive MDT inode usage, performance issues, etc.

With automatic DNE MDT space balancing (LU-13440) the need to stripe directories by default is almost completely eliminated. It should still be possible to set this by explicitly specifying --max-inherit=N, but this is too dangerous to let users shoot themselves in the foot by accident by what "seems" like a good idea but is actually very bad over time.