[LU-11190] LSOM size/age accounting histogram

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Affects Version/s: Lustre 2.12.0
• Assignee: WC Triage
• Reporter: Andreas Dilger

Description

With LSOM data being available on the MDT, it would be possible to automatically create a histogram of file sizes on the MDT. This would be useful for things like DoM planning, and other performance planning.

As each file's size is recorded, a counter in the matching power-of-two histogram bucket would be incremented, and a flag set in the LMA xattr. When a file with the LMA flag is deleted or the LSOM size is changed to a new bucket, the appropriate histogram bucket would be decremented.

It would be possible to do the same with other inode attributes (e.g. atime/mtime/ctime age histogram).

The question would be how useful it is to keep these metrics updated on every inode update vs. scanning periodically (e.g. daily or weekly) to get the information only when it is needed.

User/Group/Project quota can already track UID/GID/PRJID inode and space usage distribution.

Issue Links

• is related to: LU-13484 inode access time tables
• is related to: LU-9538 Size on MDT with guarantee of eventual consistency
• is related to: LU-12026 verify that MDS stores atime/mtime/ctime during LSOM update