[LUDOC-179] Document "dirdata" feature for upgraded filesystems

Mon, 7 Oct 2013 06:31:42 +0000

The dirdata feature should be enabled on MDT filesystems upgraded from 1.8 to 2.x using the command:

tune2fs -O dirdata /dev/{mdtdev}

This allows the FID data for each file to be stored in its directory entry and avoids a lookup of the FID in the Object Index. Without this change, the performance of accessing files is impacted significantly. The reason that this is not done automatically at upgrade time is twofold:

it can break the filesystem consistency if the filesystem is downgraded to 1.8 again and then upgraded a second time to 2.x
such actions should be controlled by the system administrator, since Lustre cannot determine itself whether the filesystem will need a downgrade to 1.8 again

We may consider for Lustre 2.6 (which will no longer be required to upgrade from 1.8 directly) to enable this feature automatically at mount time, but that should be addressed separately from documenting the current upgrade requirements.

Whamcloud Community JIRA

[LUDOC-179] Document "dirdata" feature for upgraded filesystems