Lustre 1.6 Operations Manual

32.5.8 Fast e2fsck Using the uninit_bg Feature
The uninit_bg feature helps improve e2fsck time by keeping a high watermark of
used inodes for each group. Block and inode bitmaps can be left uninitialized ondisk.
These bitmaps are tracked by flags in the group descriptor to avoid reading or
scanning them at e2fsck time. Checksums of group descriptors are maintained to
make sure that corruption of group descriptor flags does not cause uninit_bg to
operate incorrectly.
To enable uninit_bg on a new filesystem:
$ mke2fs -O uninit_bg /dev/XXX
To enable uninit_bg on an existing filesystem:
$ tune2fs -O uninit_bg /dev/XXX
$ e2fsck -fy /dev/XXX
Note – Expect many "checksum incorrect" messages.
To disable uninit_bg:
$ tune2fs -O ^uninit_bg /dev/XXX
$ e2fsck -fy /dev/XXX
Note – Expect many "checksum incorrect" messages.
Note – The uninit_bg feature is enabled, by default, with mkfs.lustre.
This feature was called "uninit_groups" in earlier Lustre-e2fsprogs releases. For
compatibility, it is still supported by tune2fs.
32-22 Lustre 1.7 Operations Manual • August 2008