On 02/14/2014 10:44 AM, Florent Bautista wrote:
Hi all,
I would like to try GlusterFS but I really don't understand how is
handled stripping and replication.
I have 3 nodes, with 1 brick each.
What can I do with that ?
I would like files stripped across the 3 servers and also files
replicated on the 3 servers. Why not can I do that ?
Then, why when adding new nodes, do we have to set multiple of {I don't
know which count} ? I mean, I want 3 replicas of every files, I have 4
servers, what is the problem ? Why GlusterFS can't balance replicas
across the available nodes ?
I could understand that putting 4 replicas into 3 nodes is problematic,
but 3 in 4 I don't understand.
With 4 bricks (brick = node + volume) and "replica 3" you'd only have a
replica of one of your bricks, the other two would not be protected.
But let's imagine that your first three bricks are 1TB disks, and the
fourth is a 3TB disk. You could split the 3TB disk, e.g. with LVM, into
three volumes to use as bricks to give you the full ×3 replication
required by gluster replication.
Also Gluster's stripe is not the same as RAID-0. While similar, it
doesn't give the performance improvement that real RAID-0 striping
gives. I'd use gluster's stripe only if I have files that are so large
they won't fit on a single brick. If you just want greater capacity for
regular files you should use distribute (dht).
--
Kaleb
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