[LU-19904] FLR-EC: compress 'trusted.lov' layout xattr to allow more components/stripes

• Type: Improvement
• Resolution: Unresolved
• Priority: Medium
• Affects Version/s: Lustre 2.17.0
• Labels: FLR-EC FLR-EC-RO FLR-EC-backlog flr-improvement hard medium
• Severity: 3
• Epic Link: FLR improvements tracker
• Assignee: WC Triage
• Reporter: Andreas Dilger

Description

The Linux VFS imposes a maximum single xattr size of XATTR_SIZE_MAX=65536 bytes, which imposes a limit on the number of stripes and/or components in a file's or directory's trusted.lov or trusted.lmv layout. The current limit is approximately a single 2000-stripe component (about 48 KiB), or 512 1-stripe components (53KiB), or some combination in between (2 mirrors of a 1300-stripe file, etc.).

It would be useful to allow the trusted.lov and trusted.lmv xattr to be saved in a compressed format (in memory, over the network and on disk) so that it could contain more components/stripes. This would be particularly useful for PFL files with multiple data components as well as multiple data mirrors and EC mirrors.