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<p>Thank you Vasily and Simon for the clarification!</p>
<p>I was looking further into it, and I got stuck with more
questions :)</p>
<p><br>
- In
<a class="moz-txt-link-freetext" href="https://www.ibm.com/support/knowledgecenter/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_hawc_tuning.htm">https://www.ibm.com/support/knowledgecenter/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_hawc_tuning.htm</a>
I read:<br>
HAWC does not change the following behaviors:<br>
write behavior of small files when the data is placed in
the inode itself<br>
write behavior of directory blocks or other metadata<br>
</p>
I wondered why? Is the metadata not logged in the (same) recovery
logs? (It seemed by reading
<a class="moz-txt-link-freetext" href="https://www.ibm.com/support/knowledgecenter/en/STXKQY_4.2.0/com.ibm.spectrum.scale.v4r2.ins.doc/bl1ins_logfile.htm">https://www.ibm.com/support/knowledgecenter/en/STXKQY_4.2.0/com.ibm.spectrum.scale.v4r2.ins.doc/bl1ins_logfile.htm</a>
it does )<br>
<br>
<br>
- Would there be a way to estimate how much of the write requests on
a running cluster would benefit from enabling HAWC ?<br>
<br>
<br>
Thanks again!<br>
<br>
Kenneth<br>
<br>
<div class="moz-cite-prefix">On 31/08/18 19:49, Vasily Tarasov
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:OF47143B1D.1BF3EEA8-ON002582FA.00607956-002582FA.0061DF44@notes.na.collabserv.com">
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<div class="socmaildefaultfont" dir="ltr"
style="font-family:Arial, Helvetica,
sans-serif;font-size:10.5pt">
<div dir="ltr">That is correct. The blocks of each recovery log
are striped across the devices in the system.log pool (if it
is defined). As a result, even when all clients have a local
device in the system.log pool, many writes to the recovery log
will go to remote devices. For a client that lacks a local
device in the system.log pool, log writes will always be
remote.</div>
<div dir="ltr"> </div>
<div dir="ltr">Notice, that typically in such a setup you would
enable log replication for HA. Otherwise, if a single client
fails (and its recover log is lost) the whole cluster fails as
there is no log to recover FS to consistent state. Therefore,
at least one remote write is essential.</div>
<div dir="ltr"> </div>
<div dir="ltr">HTH,</div>
<div dir="ltr">
<div class="socmaildefaultfont" dir="ltr"
style="font-family:Arial, Helvetica,
sans-serif;font-size:10.5pt">
<div class="socmaildefaultfont" dir="ltr"
style="font-family:Arial, Helvetica,
sans-serif;font-size:10.5pt">
<div dir="ltr">
<div>--</div>
<div>Vasily Tarasov,</div>
<div>Research Staff Member,</div>
<div>Storage Systems Research,</div>
<div>IBM Research - Almaden</div>
</div>
</div>
</div>
</div>
<div dir="ltr"> </div>
<div dir="ltr"> </div>
<blockquote data-history-content-modified="1" dir="ltr"
style="border-left:solid #aaaaaa 2px; margin-left:5px;
padding-left:5px; direction:ltr; margin-right:0px">-----
Original message -----<br>
From: Kenneth Waegeman <a class="moz-txt-link-rfc2396E" href="mailto:kenneth.waegeman@ugent.be"><kenneth.waegeman@ugent.be></a><br>
Sent by: <a class="moz-txt-link-abbreviated" href="mailto:gpfsug-discuss-bounces@spectrumscale.org">gpfsug-discuss-bounces@spectrumscale.org</a><br>
To: gpfsug main discussion list
<a class="moz-txt-link-rfc2396E" href="mailto:gpfsug-discuss@spectrumscale.org"><gpfsug-discuss@spectrumscale.org></a><br>
Cc:<br>
Subject: [gpfsug-discuss] system.log pool on client nodes for
HAWC<br>
Date: Tue, Aug 28, 2018 5:31 AM<br>
<div><font size="2" face="Default Monospace,Courier
New,Courier,monospace">Hi all,<br>
<br>
I was looking into HAWC , using the 'distributed fast
storage in client<br>
nodes' method (<br>
<a
href="https://www.ibm.com/support/knowledgecenter/en/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_hawc_using.htm"
target="_blank" moz-do-not-send="true">https://www.ibm.com/support/knowledgecenter/en/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_hawc_using.htm</a> <br>
)<br>
<br>
This is achieved by putting a local device on the clients
in the<br>
system.log pool. Reading another article<br>
(<a
href="https://www.ibm.com/support/knowledgecenter/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_syslogpool.htm"
target="_blank" moz-do-not-send="true">https://www.ibm.com/support/knowledgecenter/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_syslogpool.htm</a> <br>
) this would now be used for ALL File system recovery
logs.<br>
<br>
Does this mean that if you have a (small) subset of
clients with fast<br>
local devices added in the system.log pool, all other
clients will use<br>
these too instead of the central system pool?<br>
<br>
Thank you!<br>
<br>
Kenneth<br>
<br>
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</blockquote>
<div dir="ltr"> </div>
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