<div class="socmaildefaultfont" dir="ltr" style="font-family:Arial, Helvetica, sans-serif;font-size:10.5pt" ><div dir="ltr" >I too would second the comment about doing testing specific to your environment</div>
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<div dir="ltr" >We recently deployed a number of ESS building blocks into a customer site that was specifically being used for a mixed HPC workload.</div>
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<div dir="ltr" >We spent more than a week playing with different block sizes for both data and metadata trying to identify which variation would provide the best mix of both metadata performance and data performance. one thing we noticed very early on is that MDtest and IOR both respond very differently as you play with both block size and subblock size. What works for one use case may be a very poor option for another use case.</div>
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<div dir="ltr" >Interestingly enough it turned out that the best overall option for our particular use case was an 8MB block size with 32k sub blocks -- as that gave us good Metadata performance and good sequential data performance </div>
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<div dir="ltr" >which is probably why 32k sub block was the default for so many years ....</div>
<div dir="ltr" ><div class="socmaildefaultfont" dir="ltr" style="font-family:Arial;font-size:10.5pt" ><div class="socmaildefaultfont" dir="ltr" style="font-family:Arial;font-size:10.5pt" ><div class="socmaildefaultfont" dir="ltr" style="font-family:Arial;font-size:10.5pt" ><div dir="ltr" style="margin-top: 20px;" ><div style="font-size: 12pt; font-weight: bold; font-family: sans-serif; color: #7C7C5F;" >Andrew Beattie</div>
<div style="font-size: 10pt; font-weight: bold; font-family: sans-serif;" >Software Defined Storage - IT Specialist</div>
<div style="font-size: 8pt; font-family: sans-serif; margin-top: 10px;" ><div><span style="font-weight: bold; color: #336699;" >Phone: </span>614-2133-7927</div>
<div><span style="font-weight: bold; color: #336699;" >E-mail: </span><a href="mailto:abeattie@au1.ibm.com" style="color: #555">abeattie@au1.ibm.com</a></div></div></div></div></div></div></div>
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<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: "Marc A Kaplan" <makaplan@us.ibm.com><br>Sent by: gpfsug-discuss-bounces@spectrumscale.org<br>To: gpfsug main discussion list <gpfsug-discuss@spectrumscale.org><br>Cc:<br>Subject: Re: [gpfsug-discuss] Sub-block size not quite as expected on GPFS 5 filesystem?<br>Date: Thu, Aug 2, 2018 10:01 AM<br> <br><span style=" font-size:10pt;font-family:sans-serif" >Firstly, I do suggest that you run some tests and see how much, if any, difference the settings that are available make in performance and/or storage utilization.</span><br><br><span style=" font-size:10pt;font-family:sans-serif" >Secondly, as I and others have hinted at, deeper in the system, there may be additional parameters and settings. Sometimes they are available via commands, and/or configuration settings, sometimes not.</span><br><br><span style=" font-size:10pt;font-family:sans-serif" >Sometimes that's just because we didn't want to overwhelm you or ourselves with yet more "tuning knobs".</span><br><br><span style=" font-size:10pt;font-family:sans-serif" >Sometimes it's because we made some component more tunable than we really needed, but did not make all the interconnected components equally or as widely tunable.</span><br><span style=" font-size:10pt;font-family:sans-serif" >Sometimes it's because we want to save you from making ridiculous settings that would lead to problems...</span><br><br><span style=" font-size:10pt;font-family:sans-serif" >OTOH, as I wrote before, if a burning requirement surfaces, things may change from release to release... Just as for so many years subblocks per block seemed forever frozen at the number 32. Now it varies... and then the discussion shifts to why can't it be even more flexible?</span><br><br>
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