Ananda Bhattacharya wrote:
Hi I was wondering what the differences between gfs_tool reclaim and
gfs_tool shrink?
And secondly is there a need for these commands to be run?
-Anand
Hi Anand,
This is how I think it works (and as always, I could be wrong):
gfs_tool reclaim takes GFS metadata on disk that is no longer being
used, and
converts it back to free space. That's normally not an issue because
those unused
metadata blocks will usually be reused anyway. For example: create
files A then
file B. When you delete file A, you have an unused metadata block
for A's inode,
which has been deleted. If you allocate more space to file B, it
normally won't
reuse A's deleted inode because it's "freed metadata" rather than
"free space."
However, if your file system is out of "free space", I think a
reclaim automatically
happens and it will reuse that space anyway. Now let's say that you
create file C.
GFS can now reuse the freed metadata (inode) formally used for A, to
keep the
new metadata (inode) for C. So in either case, the deleted metadata
blocks will be
reused when GFS sees fit, and therefore, you shouldn't need to run
this command
unless you have special needs.
Incidentally, GFS2 no longer has the distinction between "free space"
and "free
metadata space", so free space is free space regardless of whether it
was previously
used for metadata or user data.
gfs_tool shrink throws out unused gfs locks from memory (cache).
Ordinarily, gfs
manages its own glocks according to the tuning parameters. So
there's really no
need to do this unless you have a special problem regarding the
caching of gfs locks.
Regards,
Bob Peterson
Red Hat Cluster Suite
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