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<p>With a replica volume the client connects and writes to all the
replicas directly. For reads, when a filename is looked up the
client checks with all the replicas and, if the file is healthy,
opens a read connection to the first replica to respond (by
default).<br>
<br>
If a server is shut down, the client receives the tcp messages
that close the connection. For read operations, it chooses the
next server. Writes will just continue to the remaining replicas
(metadata is stored in extended attributes to inform future
lookups and the self-healer of file health).<br>
<br>
If a server crashes (no tcp finalization) the volume will pause
for ping-timeout seconds (42 by default). Then continue as above.
BTW, that 42 second timeout shouldn't be a big deal. The MTBF
should be sufficiently far apart that this should still easily get
you five or six nines.<br>
</p>
<div class="moz-cite-prefix">On 8/30/22 11:55 PM, duluxoz wrote:<br>
</div>
<blockquote type="cite"
cite="mid:143833e4-3a44-c9b3-86ba-dd050c1a5d8f@gmail.com">
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<p><font size="1"><font face="Arial">Hi Guys & Gals,</font></font></p>
<p><font size="1"><font face="Arial">A Gluster newbie question for
sure, but something I just don't "get" (or I've missed in
the doco, mailing lists, etc):</font></font></p>
<p><font size="1"><font face="Arial">What happens to a Gluster
Client when a Gluster Cluster Node goes off-line /
fails-over?</font></font></p>
<p><font size="1"><font face="Arial">How does the Client "know" to
use (connect to) another Gluster Node in the Gluster
Cluster?</font></font></p>
<p><font size="1"><font face="Arial">Let me elaborate.</font></font></p>
<p><font size="1"><font face="Arial">I've got four hosts: gfs1,
gfs2, gfs3, and client4 sitting on 192.168.1.1/24, .2, .3,
and .4 respectively.</font></font></p>
<p><font size="1"><font face="Arial"><font size="1"><font
face="Arial">DNS is set up and working correctly.</font></font></font></font></p>
<p><font size="1"><font face="Arial">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 </font></font><font size="1"><font
face="Arial">gfs2:/gv1 and </font></font><font size="1"><font
face="Arial">gfs3:/gv1).</font></font></p>
<p><font size="1"><font face="Arial">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).<br>
</font></font></p>
<p><font size="1"><font face="Arial">So, (and I haven't tested
this yet) what happens to </font></font><font size="1"><font
face="Arial">client4:/data/gv1/file1 when gfs1 fails (ie is
turned off, crashes, etc)?</font></font></p>
<p><font size="1"><font face="Arial">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?</font></font></p>
<p><font size="1"><font face="Arial">I thought about setting some
DNS entries along the lines of:</font></font></p>
<p><font size="1"><font face="Arial">~~~<br>
</font></font></p>
<p><font size="1"><font face="Arial">glustercluster IN A
192.168.0.1<br>
</font></font></p>
<p><font size="1"><font face="Arial"><font size="1"><font
face="Arial">glustercluster IN A 192.168.0.2</font></font></font></font></p>
<p><font size="1"><font face="Arial"><font size="1"><font
face="Arial"><font size="1"><font face="Arial">glustercluster
IN A 192.168.0.3</font></font></font></font></font></font></p>
<p><font size="1"><font face="Arial">~~~<br>
</font></font></p>
<p><font size="1"><font face="Arial">and having </font></font><font
size="1"><font face="Arial">clients4's /etc/fstab file read: "</font></font><font
size="1"><font face="Arial">glustercluster</font></font><font
size="1"><font face="Arial"><font size="1"><font face="Arial">:gv1
/data/gv1 glusterfs defaults 0 2</font></font>", but
this is a Round-Robin DNS config and I'm not sure how
Gluster treats this situation.</font></font></p>
<p><font size="1"><font face="Arial">So, if people could comment /
point me in the correct direction I would really appreciate
it - thanks.</font></font></p>
<p><font size="1"><font face="Arial">Dulux-Oz<br>
</font></font></p>
<br>
<fieldset class="moz-mime-attachment-header"></fieldset>
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