[LU-1167] Poor mdtest unlink performance with multiple processes per node

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Affects Version/s: Lustre 2.1.1
• Environment: SL6.1,; 2.6.32-131.12.1.el6.lustre.20.x86_64
• Severity: 3

Epic

metadata performance

• Assignee: WC Triage
• Reporter: Nathan Rutman

Description

We have noticed in testing that running multiple mdtest processes per node severely degrades unlink performance.

• Lustre mounted once per client; not multimount.
• shared directory case
  This can be seen at a wide range of node counts (5-128) and backends, to varying degrees.
  Interestingly scaling the client count up does not seem to have nearly the same negative performance impact; only the ppn seems to matter.

	total
nodes	jobs	unlink kops
8	8	11.4
8	16	9.7
8	32	8.6
8	64	7

We see the same issue with 1.8.6 clients against the server; we do not see it with 1.8.6 servers.

Issue Links

• is related to: LU-3308 large readdir chunk size slows unlink/"rm -r" performance
• is related to: LU-1695 Demonstrate MDS performance with increasing client load for SMP Affinity