<div class="socmaildefaultfont" dir="ltr" style="font-family:Arial, Helvetica, sans-serif;font-size:10.5pt" ><div dir="ltr" >Simon,</div>
<div dir="ltr" > </div>
<div dir="ltr" >My recommendation is still very much to use SSD for Metadata and NL-SAS for data and</div>
<div dir="ltr" >the GH14 / GH24 Building blocks certainly make this much easier.</div>
<div dir="ltr" > </div>
<div dir="ltr" >Unless your filesystem is massive (Summit sized) you will typically still continue to benefit from the Random IO performance of SSD (even RI SSD) in comparison to NL-SAS.</div>
<div dir="ltr" > </div>
<div dir="ltr" >It still makes more sense to me to continue to use 2 copy or 3 copy for Metadata even in ESS / GNR style environments. The read performance for metadata using 3copy is still significantly better than any other scenario.</div>
<div dir="ltr" > </div>
<div dir="ltr" >As with anything there are exceptions to the rule, but my experiences with ESS and ESS with SSD so far still maintain that the standard thoughts on managing Metadata and Small file IO remain the same -- even with the improvements around sub blocks with Scale V5.</div>
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<div dir="ltr" >MDtest is still the typical benchmark for this comparison and MDTest shows some very clear differences even on SSD when you use a large filesystem block size with more sub blocks vs a smaller block size with 1/32 subblocks</div>
<div dir="ltr" > </div>
<div dir="ltr" >This only gets worse if you change the storage media from SSD to NL-SAS</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" data-history-expanded="1" dir="ltr" style="border-left:solid #aaaaaa 2px; margin-left:5px; padding-left:5px; direction:ltr; margin-right:0px" >----- Original message -----<br>From: Simon Thompson <S.J.Thompson@bham.ac.uk><br>Sent by: gpfsug-discuss-bounces@spectrumscale.org<br>To: "gpfsug-discuss@spectrumscale.org" <gpfsug-discuss@spectrumscale.org><br>Cc:<br>Subject: [gpfsug-discuss] Metadata with GNR code<br>Date: Fri, Sep 21, 2018 3:29 AM<br> <br><!--Notes ACF
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<div><p><span style="font-size:11.0pt" >Just wondering if anyone has any strong views/recommendations with metadata when using GNR code?<o:p></o:p></span></p>
<p><span style="font-size:11.0pt" ><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt" >I know in “san” based GPFS, there is a recommendation to have data and metadata split with the metadata on SSD.<o:p></o:p></span></p>
<p><span style="font-size:11.0pt" ><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt" >I’ve also heard that with GNR there isn’t much difference in splitting data and metadata.<o:p></o:p></span></p>
<p><span style="font-size:11.0pt" ><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt" >We’re looking at two systems and want to replicate metadata, but not data (mostly) between them, so I’m not really sure how we’d do this without having separate system pool (and then NSDs in different failure groups)….<o:p></o:p></span></p>
<p><span style="font-size:11.0pt" ><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt" >If we used 8+2P vdisks for metadata only, would we still see no difference in performance compared to mixed (I guess the 8+2P is still spread over a DA so we’d get half the drives in the GNR system active…).<o:p></o:p></span></p>
<p><span style="font-size:11.0pt" ><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt" >Or should we stick SSD based storage in as well for the metadata pool? (Which brings an interesting question about RAID code related to the recent discussions on mirroring vs RAID5…)<o:p></o:p></span></p>
<p><span style="font-size:11.0pt" ><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt" >Thoughts welcome!<o:p></o:p></span></p>
<p><span style="font-size:11.0pt" ><o:p> </o:p></span></p>
<p><span style="font-size:11.0pt" >Simon<o:p></o:p></span></p></div>
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