[Gluster-users] How Does Gluster Failover

[duluxoz]

Hi Guys & Gals,

A Gluster newbie question for sure, but something I just don't "get" (or 
I've missed in the doco, mailing lists, etc):

What happens to a Gluster Client when a Gluster Cluster Node goes 
off-line / fails-over?

How does the Client "know" to use (connect to) another Gluster Node in 
the Gluster Cluster?

Let me elaborate.

I've got four hosts: gfs1, gfs2, gfs3, and client4 sitting on 
192.168.1.1/24, .2, .3, and .4 respectively.

DNS is set up and working correctly.

gfs1, gs2, and gfs3 form a "Gluster Cluster" with a Gluster Volume (gv1) 
replicated across all three nodes. This is all working correctly (ie a 
file (file1) created/modified on gfs1:/gv1 is replicated correctly to 
gfs2:/gv1 and gfs3:/gv1).

client4 has an entry in its /etc/fstab file which reads: "gfs1:gv1  
/data/gv1  glusterfs defaults  0 2". This is also all working correctly 
(ie client4:/data/gv1/file1 is accessible and replicated).

So, (and I haven't tested this yet) what happens to 
client4:/data/gv1/file1 when gfs1 fails (ie is turned off, crashes, etc)?

Does client4 "automatically" switch to using one of the other two 
Gluster Nodes, or do I have something wrong in clients4's /etc/fstab 
file, or an error/mis-configuration somewhere else?

I thought about setting some DNS entries along the lines of:

~~~

glustercluster  IN  A 192.168.0.1

glustercluster  IN  A  192.168.0.2

glustercluster IN  A  192.168.0.3

~~~

and having clients4's /etc/fstab file read: "glustercluster:gv1 
/data/gv1  glusterfs  defaults  0 2", but this is a Round-Robin DNS 
config and I'm not sure how Gluster treats this situation.

So, if people could comment / point me in the correct direction I would 
really appreciate it - thanks.

Dulux-Oz
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