[Gluster-users] thoughts on disk usage (df) output

Keith Freedman
Sun, 03 Aug 2008 03:02:02 -0000

This probably is better posed in the gluster-devel mailing list, and
it's not a big deal and probably not something that needs to be
solved, but I felt i should share the situation, just in case anyone
else needs to do the same thing.


So, I have 2 servers AFRing eachother.  They had the same amount of
disk space but on different sized drives.
Since gluster just sits on top of the underlying filesystem, what I did was:

/dev/disk1 mounts to /gluster
/dev/disk2 mount to /gluster/extra

in the gluster translator, I specify the source path as /gluster and
mount it to /home

so in home I now see /home/extra and /home/(all the other dirs)
This works fine AFR seems to be happy.

When I do a df, however, /home is reported as the same as /dev/disk1
rather than the combined values of /dev/disk1 and /dev/disk2
I certainly understand why, and realize it'd be quite difficult to
resolve this issue.

It's not very full, so my concern is..  might gluster
overfill  /home/extra because it thinks it has more space than it
does, or might it think the disk is full when it's not and there's
still room to write files (if they're being written in /home/extra).

As a testament to gluster.. this non-standard configuration does seem
to work just fine, and the  underlying file systems are actually even
different..  one is xfs the other is ext3 (mounted with user_xattr option).

Ultimately, I'll sanitize this configuration, but the fact that it
works so well now is impressive.

Keith