[LU-14762] qos subdirectory creation stay on parent MDT if less full than average doesn't work as expected

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.15.0
• Severity: 3
• Assignee: Lai Siyao
• Reporter: Lai Siyao

Description

In "space balanced" subdirectory creation, subdirectories are kept on the parent MDT if it is less full than average, but it use "weight" other than space, however

weight = free space - penalty

if MDTs have different penalties, it will make this inaccurate.

Issue Links

• is duplicated by: LU-14659 sanity test_413a: subdirs shouldn't be evenly distributed
• is related to: LU-13439 DNE3: MDT QOS tuning to avoid full MDTs completely
• is related to: LU-13440 DNE3: limit directory default layout inheritance
• is related to: LU-15850 MDT QOS should always be used for round-robin directories.