[Gluster-users] missing bricks

Todd Pfaff pfaff at mcmaster.ca
Sun Jan 1 16:34:35 UTC 2012

I'm currently experimenting with gluster in a way that may be an unusual
use case.  We have a single system with 45 cheap sata drives which we use
for disk-to-disk backups only.

For the past two years we have been using this system with linux software
raid, with the drives organized as multiple raid 5/6/10 sets of 5 drives
per set.  This has worked ok but we've suffered through enough multiple
simultaneous drive failures to prompt me to explore alternatives to raid.
Yes, I know, that's what we get for using cheap drives.

What I'm experimenting with now is creating gluster distributed-replicated
volumes on some of these drives.  At this point I am using 10 drives
configured as shown here:

   Volume Name: volume1
   Type: Distributed-Replicate
   Status: Started
   Number of Bricks: 5 x 2 = 10
   Transport-type: tcp
   Brick1: host:/gluster/brick01
   Brick2: host:/gluster/brick06
   Brick3: host:/gluster/brick02
   Brick4: host:/gluster/brick07
   Brick5: host:/gluster/brick03
   Brick6: host:/gluster/brick08
   Brick7: host:/gluster/brick04
   Brick8: host:/gluster/brick09
   Brick9: host:/gluster/brick05
   Brick10: host:/gluster/brick10
   Options Reconfigured:

host is, and host is both the gluster server and client.

For the most part this is working fine so far.  The problem I have run
into several times now is that when a drive fails and does not come back
online when the system is rebooted, the volume comes up without that
brick.  Gluster then happily writes to the missing brick's mount point,
thereby eventually filling up the root filesystem.  Once the root
filesystem is full and processes writing to gluster space are hung, I can
never recover from this state without rebooting.

Is there any way to avoid this problem of gluster writing to a brick
path that isn't really populated by the intended brick filesystem?
Does gluster not create any sort of signature or meta-data that
indicates whether or not a path is really a gluster brick?

I realize that ultimately I should get the bricks replaced as soon as
possible but there may be times when I want to continue running for some
time with a "degraded" volume if you will.

All ideas, suggestions, comments, criticisms are welcome.


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