[Gluster-users] Some more questions

[Gandalf Corvotempesta]

Ok, some more question as I'm still planning our SDS (but I'm prone to use
LizardFS, gluster is too inflexible)

Let's assume a replica 3:

1) currently, is not possbile to add a single server and rebalance like any
order SDS (Ceph, Lizard, Moose, DRBD, ....), right ? In replica 3, I have
to add 3 new servers

2) The same should be by add disks on spare slots on existing servers.
Always a multiple of replica count, thus 1 disk per server

3) Can I grow the cluster by replacing 3 disks with bigger ones? In
example, with 12 2TB disks (on each server), I can replace 3 of them (1 per
server) with 4TB to get more space, right ? Or should I replace *all* disks
?

[Gandalf Corvotempesta]

You can change the replica count. Add a fourth server, add it's brick to

existing volume with gluster volume add-brick vol0 replica 4
newhost:/path/to/brick

This doesn't add space, but only a new replica, increasing the number of
copies

[Jim Kinney]

correct. a new server will NOT add space in this manner. But the
original Q was about rebalancing after adding a 4th server. If you are
using distributed/replication, then yes, a new server with be adding a
portion of it's space to add more space to the cluster.
But in a purely replica mode, nope.

Post by Gandalf Corvotempesta
com>

You can change the replica count. Add a fourth server, add it's brick to

existing volume with gluster volume add-brick vol0 replica 4
newhost:/path/to/brick
This doesn't add space, but only a new replica, increasing the number of
copies

[Jim Kinney]

It all depends on how you are set up on the distribute. Think RAID 10
with 4 drives - each pair strips (distribute) and the pair of pairs
replicates.

com>

Post by Jim Kinney
correct. a new server will NOT add space in this manner. But the
original

Q was about rebalancing after adding a 4th server. If you are using
distributed/replication, then yes, a new server with be adding a
portion of
it's space to add more space to the cluster.
Wait, in a distribute-replicate, with replica count 3, adding a
fourth
server doesn't add space..... I can't add a fourth server, I have to
add 3
more servers (due to the replica count)

[Gandalf Corvotempesta]

Post by Jim Kinney
It all depends on how you are set up on the distribute. Think RAID 10

with 4 drives - each pair strips (distribute) and the pair of pairs
replicates.

Exactly, thus I have to add the same replica count.
In a RAID10, you have to add 2 disk at once. Or in a 3way RAID10 you have
to add 3 disks at once and so on.