[LU-18891] increase default DNE MDT "lfs setdirstripe --max-inherit-rr"

• Type: Improvement
• Resolution: Unresolved
• Priority: Major
• Labels: easy
• Severity: 3
• Assignee: Core Lustre Triage
• Reporter: Andreas Dilger

Description

Recent testing has shown that increasing the default round-robin depth for directories created near the root directory from the current default of 3 to some higher depth (5/6) or larger can improve performance for larger filesystems.

However, care must be taken to avoid adding unnecessary overhead for systems with only a small number of MDTs, because creating a remote directory can take up to 10x longer to finish.

It may be that the ideal situation is to tune the max-inherit-rr value set on the root directory based on the number of MDTs formatted in the filesystem. If the number of MDTs is 10+ then the extra overhead for creating remote directories is compensated by the improved performance from getting more MDTs involved. Otherwise, something like "3 + MDT_COUNT" might be reasonable.

Issue Links

• is related to: LU-19424 show/set LMV MDT mkdir starting index