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<div class="moz-cite-prefix">On 2021-08-05 5:53 p.m., Janusz
Jaskiewicz wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAGf4UHCFcThXBFuO0h==Xufb9=op3cg-qxEZXakFP3MgDJd_=w@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Hello.<br>
<br>
I'm experimenting a bit with DRBD in a cluster managed by
Pacemaker.<br>
It's a two node, active-passive cluster and the service that I'm
trying to put in the cluster writes to the file system.<br>
The service manages many files, it appends to some of them and
increments the single integer value in others.<br>
<br>
I'm observing surprising behaviour and I would like to ask you
if what I see is expected or not (I think not).<br>
<br>
I'm using protocol C, but still I see some delay in the files
that are being replicated to the secondary server.<br>
For the files that increment the integer I see a difference
which corresponds roughly to 1 second of traffic.<br>
<br>
I'm really surprised to see this, as protocol C should guarantee
synchronous replication.<br>
I'd rather expect some delay in processing (potentially slower
disk writes due to the network replication).<br>
<br>
The way I'm testing it:<br>
The service runs on primary and writes to DRBD drive, secondary
connected and "UpToDate".<br>
I kill the service abruptly (kill -9) and then take down the
network interface between primary and secondary (kill and ifdown
commands in the script so executed quite promptly one after the
other).<br>
Then I mount the DRBD drive on both nodes and check the
difference in the files with incrementing integer.<br>
<br>
I would appreciate any help or pointers on how to fix this.<br>
But first of all I would like to confirm that this behaviour is
not expected.<br>
<br>
Also if it is expected/allowed, how can I decrease the impact? <br>
<br>
<br>
<br>
Please find below my configuration:<br>
<br>
global_common.conf:<br>
<br>
global {<br>
usage-count yes;<br>
udev-always-use-vnr; # treat implicit the same as explicit
volumes<br>
}<br>
<br>
common {<br>
handlers {}<br>
startup {}<br>
options {}<br>
disk {}<br>
net {<br>
protocol C;<br>
}<br>
}<br>
<br>
<br>
<br>
my_resource.conf:<br>
<br>
resource wyr-dim-persistence {<br>
on <a href="http://dimprod01.my.clustertest.com"
moz-do-not-send="true">dimprod01.my.clustertest.com</a> {<br>
device /dev/drbd1;<br>
disk /dev/mapper/drbdpool-drbdata;<br>
address <a href="http://192.168.0.1:7789"
moz-do-not-send="true">192.168.0.1:7789</a>;<br>
meta-disk internal;<br>
}<br>
on <a href="http://dimprod02.my.clustertest.com"
moz-do-not-send="true">dimprod02.my.clustertest.com</a> {<br>
device /dev/drbd1;<br>
disk /dev/mapper/drbdpool-drbdata;<br>
address <a href="http://192.168.0.2:7789"
moz-do-not-send="true">192.168.0.2:7789</a>;<br>
meta-disk internal;<br>
}<br>
}</div>
</blockquote>
<p>What filesystem are you using? Is it cluster / multi-node aware?<br>
</p>
<p><br>
</p>
<pre class="moz-signature" cols="72">--
Digimer
Papers and Projects: <a class="moz-txt-link-freetext" href="https://alteeve.com/w/">https://alteeve.com/w/</a>
"I am, somehow, less interested in the weight and convolutions of Einstein’s brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops." - Stephen Jay Gould</pre>
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