On 08/29/2012 03:17 PM, Johnny Hughes wrote: > On 08/29/2012 08:06 AM, Les Mikesell wrote: >> On Wed, Aug 29, 2012 at 7:49 AM, Johnny Hughes <johnny at centos.org> wrote: >>>> If we were rich, I guess we would have two (or more) "geo-replicated" glusters and >>>> be able to withstand one failing... >>>> I would like the same trust level that I have in RAID. >>> I have routinely used DRBD for things like this ... 2 servers, one a >>> complete failover of the other one. Of course, that requires a 50+ TB >>> file system on each machine. >> How well do glusterfs or drbd deal with downtime of one of the >> members? Do they catch up quickly with incremental updates and what >> kind of impact does that have on performance as it happens? And is >> either suitable for running over distances where there is some network >> latency? >> > > Well, DRBD is a tried and true solution, but it requires dedicated boxes > and crossover network connections, etc. I would consider it by far the > best method for providing critical failover. > > I would consider gluserfs almost a different thing entirely ... it > provides the ability to string several partitions on different machines > into one shared network volume. > > Glusterfs does also provide redundancy if you set it up that way ... and > if you have a fast network and enough volumes then the performance is > not very degraded when a gluster volume comes back, etc. > > However, I don't think I would trust extremely critical things on > glusterfs at this point. I think the keyword with solutions like glusterfs, ceph, sheepdog, etc. is "elasticity". DRBD and RAID work well as long as you have a fixed size of data to deal with but once you get to a consistent data growth you need something that offers redundancy yet can be easily extended incrementally. Glusterfs seems to aim to be a solution that works well right now because it uses a simple file replication approach whereas ceph and sheepdog seem to go deeper and provide better architectures but will take longer to mature. Regards, Dennis