[DRBD-user] drbd vs GFS/GNDB

Stefan Andersson kollen_79 at nosplease.com
Fri Jul 2 20:15:55 CEST 2004

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hello,

I'm in the process of building a fault tolerant system, and
have looked at drbd and the recent GFS release by redhat.

What I ideally would like to have is

1. one filesystem shared among a number of nodes, with write
   access at all nodes. "shared storage" (shared scsi) would
   introduce a single point of failure, so I'm thinking more
   in the lines of storage replication, i.e. what drbd is doing.

2. arbitrary node(s) may fail, and be resynchronized after repair

3. good performance

Now, as I understand drbd works only in a primary/secondary
configuration, where all writes at paul/primary is replicated to
silas/secondary, and their roles can switch with heartbeat software.

The two node configuration may be sufficient for our needs, but it
would be a nice bonus to be able to mount the file system from three,
four nodes. Will perhaps GNBD (gfs network block device) solve this
instead of using drbd? (but, as far as I can tell, it will only have
one primary and is mainly for load balancing and not fault tolerance)

Would it be possible to use GFS on top of DRBD to get write support at
both nodes? I.e. does drbd replicate writes at silas to paul?

Another acceptable solution would be to use for example ext3 on the drbd
replicated block device. Now, I've understood that it is not adviced to mount
the filesystems at the secondary node because the FS will change under
its feed because it is not aware of another host writing. My question
is, would it be possible to mount the filesystem readonly at silas?
This would ease the burden of backup on the primary node as they instead
could be done on the secondary node.

Thoughts?

Regards,
 Stefan





More information about the drbd-user mailing list