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Hello again,<br>
<br>
After comparing DRBD 8.3 and 8.4 source code, I see that conditional
TCP_CORK-ing remains to be done in 8.4. Can it be the reason why we
experiment PingAck problems on idle resources ?<br>
<br>
PS: our cluster was running DRBD 8.3 beforehands and we had no such
problem... but we were also using Infiniband SDP instead of IPoIB
(so we can not know whether the problem really lies with DRBD).<br>
<br>
Thanks for your insights,<br>
<br>
Cédric<br>
<br>
<div class="moz-cite-prefix">On 02/02/14 21:29, Cédric Dufour -
Idiap Research Institute wrote:<br>
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Hello,<br>
<br>
We are experiencing "PingAck timeout" on a system where multiple
DRBD resources are configured (more exactly a pair of
active/active Lustre MDS servers):<br>
<br>
A --- drbd0 --- B [nfs-data] idle<br>
A --- drbd1 --- B [nfs-apps] idle<br>
A --- drbd2 --- B [nfs-tmp] idle<br>
A --> drbd3 --> B [mdt1] heavy load<br>
A <-- drbd4 <-- B [mdt2] heavy load<br>
A --- drbd5 --- B [mgs] idle<br>
<br>
Our environment is DRBD 8.4.4, with "ping-int = 10s" and
"ping-timeout = 25" (2.5s)<br>
<br>
The link between the two servers is 20Gb/s Infiniband (configured
in datagram mode).<br>
<br>
Strangely, the timeout occurs on an idle resource (e.g. drbd1)
when two of the other resources ('mdt1' and 'mdt2') are heavily
loaded (and displaying no connection/timeout problem
what-so-ever).<br>
<br>
Looking at the source code, I believe that DRBD cannot know about
the potentially "congested" link (because of the heavily loaded
resources, 'mdt1' and 'mdt2') and the potentially resulting
PingAck timeout it may spawn for another idle one (e.g. 'drbd1').
Am I right ?<br>
<br>
Is there a way to circumvent this problem ?<br>
<br>
Thanks and best,<br>
<br>
Cédric Dufour<br>
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<p>Cédric Dufour @ Idiap Research Institute</p>
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