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<p>You know when you do a `gluster volume info` and you get the
whole volume definition, the client graph is built from the same
info. In fact, if you look in /var/lib/glusterd/vols/$volume_name
you'll find some ".vol" files. `$volume_name.tcp-fuse.vol` is the
configuration that the clients receive from whichever server they
initially connect to. You'll notice that file has multiple
"type/client" sections, each establishing a tcp connection to a
server.<br>
<br>
Sidenote: You can also see in that file, how the microkernels are
used to build all the logic that forms the volume, which is kinda
cool. Back when I first started using gluster, there was no
glusterd and you have to build those .vol files by hand.<br>
</p>
<div class="moz-cite-prefix">On 8/31/22 8:04 AM, Matthew J Black
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:e8183f56-c910-7403-c607-e9aa5143fa05@gmail.com">
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<p><font face="Times New Roman, Times, serif">Hi Joe,</font></p>
<p><font face="Times New Roman, Times, serif">Thanks for getting
back to me about this, it was helpful, and I really appreciate
it.</font></p>
<p><font face="Times New Roman, Times, serif">I am, however, still
(slightly) confused - *how* does the client "know" the
addresses of the other servers in the cluster (for read or
write purposes), when all the client has is the line in the
fstab file: "</font><font face="Times New Roman, Times, serif"><font
size="1"><font face="Arial">gfs1:gv1 /data/gv1 glusterfs
defaults 0 2</font></font>"? I'm missing something,
somewhere, in all of this, and I can't work out what that
"something" is. :-)</font></p>
<p><font face="Times New Roman, Times, serif">Your help truely is
appreciated</font></p>
<p><font face="Times New Roman, Times, serif">Cheers</font></p>
<p><font face="Times New Roman, Times, serif">Dulux-Oz</font><br>
</p>
<div class="moz-cite-prefix">
<title>PEREGRINE IT Signature</title>
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On 01/09/2022 00:55, Joe Julian wrote:<br>
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cite="mid:712baf67-b380-7164-56a4-5f5dc1cb92f6@julianfamily.org">
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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>
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