On Thu, Apr 14, 2011 at 02:20:02PM -0700, Mohit Anchlia wrote: > Which similar systems are you referring to? DR:BD has an overlapping use case, although it's pretty much constrained to mirroring between two storage systems. And it has options to return to the user after either writing to the first system, or only after writing to the second - or even _before_ writing to the first if you trust that once it has the data it will get there. DR:BD's also more typically used in primary-secondary arrangements for failover than in primary-primary arrangements for load sharing. But there are ways to do the second. I've got one pair of servers mirrored through DR:BD proving file storage via NFS, and another pair now running Gluster, also providing NFS service. Both are doing well so far, although my Gluster use is only a few days, where DR:BD's been running happily for months. Gluster is easier to configure, as DR:BD takes cryptic commands, and requires combination with other daemons to get the job done. But DR:BD is very good at what it does, and well documented - except that you've got to cobble together its documentation with that of the other daemons you're integrating it with to get your result, which can be a bit of a mental stretch (at least for me). DR:BD also, being at the device level and in the kernel, has advantages in stacking with other stuff. I can put a KVM in an LVM on DR:BD - and KVMs do well as LVMs, both running efficiently in them and allowing LVM snapshotting - it's a better format than qcow. As I understand it I can't put an LVM on top of a Gluster - although it has no problem using ext4-formatted LVMs as bricks, I doubt it can work in any way with LVMs which are KVMs, with no file system in between. Despite that I'm trying to work out the logic of how to put an HA KVM setup on a 2-unit replicated Gluster system. It should be possible to get both failover, and live-migration failback going, once I get the concepts and incantations right. While KVM is solid, its docs are terse and incomplete. That seems to be a trend. Book publishers no longer rush out books on the latest tech, and free software creators who hold back instructions improve their chance of consulting contracts. Whit
