HAMMER version 2 ready for testing on master branch
HAMMER now supports upgrading to version 2 via the hammer
version-upgrade directive. This is currently only available on the
master development branch. Though I am confident that I won't break the
filesystem, please only upgrade if you are willing to lose the FS.
After a week or so the feature should be tested well enough.
When upgrading using the 'hammer version-upgrade <fs> 2' directive, be
sure you are running the latest and greatest from the master branch.
If you are running an older HAMMER, the version-upgrade will fail with
an error. DO NOT FORCE IT. Do not use the 'force' directive. If you
do this with an old HAMMER VFS you will get an old WIP and break your
filesystem. Use 'hammer version <fs>' to list available versions and
be sure that that version 2 is marked 'NORM', not 'WIP'.
Note that the older version 1 HAMMER VFS will not be able to read
directories created by version 2. Also note that directories which
existed prior to the upgrade will still use the old layout.
--
Once upgraded, any new directories created in the HAMMER fs will place
the directory entry B-Tree elements in the same B-Tree localization
domain as the inode elements. This change significantly improves 'find'
and 'ls -lR' times, and moderately improves tar-up and cpdup times.
However, the initial B-Tree layout is still horrendously bad so you will
not see the improvement with newly laid-down directory trees until after
you reblock the btree via 'hammer reblock-btree'. I'm working on the
initial B-Tree layout issue. Ultimately, though, it's not a big deal
since the B-tree is reblocked daily anyway.
Tests (after reblock-btree) on 20 copies of /usr/src: 862924 files / 15GB:
test29:/root# /usr/bin/time find /mnt/test.<blah> | wc -l
45.49 real 0.60 user 5.91 sys OLD
28.73 real 0.57 user 4.92 sys NEW
(58% improvement)
test29:/root# /usr/bin/time find /mnt/test.<blah> -ls | wc -l
49.74 real 3.74 user 18.41 sys OLD
36.28 real 3.71 user 17.98 sys NEW
(37% improvement)
test29:/root# /usr/bin/time tar cf - /mnt/test.<blah> | wc -c
820.87 real 10.53 user 94.41 sys OLD
745.51 real 9.81 user 92.86 sys NEW
(10% improvement)
-Matt
Matthew Dillon
<dillon@backplane.com>