[Gluster-users] Is mirroring provides failover protection?

[Andrew Séguin]

Hi,

Assuming the replication works fine (you see the files on both servers
A and B) and that you use the Gluster client (mount -t glusterfs ...),
then if server A goes down, your application will continue seamlessly
to use server B although you could encounter problems later:

If the server with your application has to restart, and server A is
down at that moment, then unfortunately the gluster client does not
connect to a gluster server, and does not get to know that server B
exists.

To avoid that problem, you can prepare your Gluster cluster system
with 3 IP addresses: server A, server B, and a "shared" IP for the two
nodes which will be active only on one of the two servers at a time.
Some system then has to decide which server is currently master -- the
CARP protocol could be of help here. Maybe the following blog/howto
would be of help for this:
http://www.misdivision.com/blog/setting-up-a-highly-available-storage-cluster-using-glusterfs-and-ucarp

With NFS & CIFS the clients don't know about the second server, in
case you do not have a shared IP, the connection would be broken. NFS
without the shared IP is the same as having an offline backup but with
the advantage that the backup is up to date.

While I'm not a gluster expert, I hope this helps!
Andrew


On Sat, Jan 15, 2011 at 2:03 AM, Sergiy Lozovsky
<serge_lozovsky at yahoo.com> wrote:
> Hi,
>
> I have two Gluster servers A and B. They are mirrored. I mount A. What happens when server A goes down?
>
> I would like for my applications to seamlessly use data from the Gluster storage B.
>
> Thanks,
>
> Sergiy.
>
>
>
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