[LUDOC-223] Is the "FID-in-dirent" feature (ie. tunefs -O dirdata) is backwards compatible with 1.8.9 clients?

• Status: Resolved
• Project: Lustre Documentation
• Type: Bug
• Priority: Major
• Reporter: Oz Rentas
• Assignee: Jodi Levi (Inactive)
• Resolution: Fixed

Environment

Lustre 2.1.5 MDS/OSS
Lustre 1.8.9 Clients

• Severity: 2

Description

Yale just recently upgrade their MDS and OSS servers running 2.1.5 (upgraded from 1.8.9). However, the client are still running 1.8.9.

Although it has been stated 1.6+ clients understand the new FID format, the 2.x lustre operations manual at hpdd-intel doesn't explicitly say it will work with older clients. They would like clarification on if the "FID-in-dirent" feature (ie. tunefs -O dirdata) is backwards compatible with 1.8.9 clients ?

Also, is there high risk involved enabling "dirdata" when running old 1.8.9 clients ? Any opinions if there is benefit in using this flag ?

Comments

[Shuichi Ihara (Inactive)]

hmm.. Oz, I don't think this is Lustre Doc issue. we should change "issue type"..

[Oz Rentas]

Andreas responded to this one on HDPP-discuss:

The fid-in-dirent feature is only relevant on the MDT. It does not directly affect the client or OST, but will affect the performance that the client sees when accessing files created under 2.x.

There is a noticeable performance improvement (or more specifically no performance degradation) for 2.x files with this feature enabled. The main reason it is not enabled by default is that it impacts the ability to downgrade to 1.8 again safely. Once you know you don't want to downgrade again it is ok to enable it.

Please close ticket.

Thanks,
Oz

[John Fuchs-Chesney (Inactive)]

Marked as resolved per partner's guidance.
~ jfc.