<div class="socmaildefaultfont" dir="ltr" style="font-family:Arial, Helvetica, sans-serif;font-size:12pt" ><div dir="ltr" style="font-family:Arial, Helvetica, sans-serif;font-size:12pt" ><div dir="ltr" >Hi</div>
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<div dir="ltr" >There other reasons to have more than 1. It is management of those. When you have to add or remove NSDs of a FS having more than 1 makes it possible to empty some space and manage those in and out. Manually but possible. If you have one big NSD or even 1 per enclosure it might difficult or even not possible depending the number of enclosures and FS utilization.</div>
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<div dir="ltr" >Starting some ESS version (not DSS, cant comment on that) that I do not recall but in the last 6 months, we have change the default (for those that use the default) to 4 NSDs per enclosure for ESS 5000. There is no impact on performance either way on ESS, we tested it. But management of those on the long run should be easier.</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: "Achim Rehor" <Achim.Rehor@de.ibm.com><br>Sent by: gpfsug-discuss-bounces@spectrumscale.org<br>To: gpfsug main discussion list <gpfsug-discuss@spectrumscale.org><br>Cc:<br>Subject: [EXTERNAL] Re: [gpfsug-discuss] dssgmkfs.mmvdisk number of NSD's<br>Date: Mon, Mar 1, 2021 10:16<br>
<div><font size="2" face="Default Monospace,Courier New,Courier,monospace" >The reason for having multiple NSDs in legacy NSD (non-GNR) handling is<br>the increased parallelism, that gives you 'more spindles' and thus more<br>performance.<br>In GNR the drives are used in parallel anyway through the GNRstriping.<br>Therfore, you are using all drives of a ESS/GSS/DSS model under the hood<br>in the vdisks anyway.<br><br>The only reason for having more NSDs is for using them for different<br>filesystems.<br><br> <br>Mit freundlichen Grüßen / Kind regards<br><br>Achim Rehor<br><br>IBM EMEA ESS/Spectrum Scale Support<br><br><br><br><br><br><br><br><br><br><br><br><br>gpfsug-discuss-bounces@spectrumscale.org wrote on 01/03/2021 08:58:43:<br><br>> From: Jonathan Buzzard <jonathan.buzzard@strath.ac.uk><br>> To: gpfsug-discuss@spectrumscale.org<br>> Date: 01/03/2021 08:58<br>> Subject: [EXTERNAL] Re: [gpfsug-discuss] dssgmkfs.mmvdisk number of<br>NSD's<br>> Sent by: gpfsug-discuss-bounces@spectrumscale.org<br>><br>> On 28/02/2021 09:31, Jan-Frode Myklebust wrote:<br>> ><br>> > I?ve tried benchmarking many vs. few vdisks per RG, and never could<br>see<br>> > any performance difference.<br>><br>> That's encouraging.<br>><br>> ><br>> > Usually we create 1 vdisk per enclosure per RG, thinking this will<br>> > allow us to grow with same size vdisks when adding additional<br>enclosures<br>> > in the future.<br>> ><br>> > Don?t think mmvdisk can be told to create multiple vdisks per RG<br>> > directly, so you have to manually create multiple vdisk sets each with<br><br>> > the apropriate size.<br>> ><br>><br>> Thing is back in the day so GPFS v2.x/v3.x there where strict warnings<br>> that you needed a minimum of six NSD's for optimal performance. I have<br>> sat in presentations where IBM employees have said so. What we where<br>> told back then is that GPFS needs a minimum number of NSD's in order to<br>> be able to spread the I/O's out. So if an NSD is being pounded for reads<br><br>> and a write comes in it. can direct it to a less busy NSD.<br>><br>> Now I can imagine that in a ESS/DSS-G that as it's being scattered to<br>> the winds under the hood this is no longer relevant. But some notes to<br>> the effect for us old timers would be nice if that is the case to put<br>> our minds to rest.<br>><br>><br>> JAB.<br>><br>> --<br>> Jonathan A. Buzzard Tel: +44141-5483420<br>> HPC System Administrator, ARCHIE-WeSt.<br>> University of Strathclyde, John Anderson Building, Glasgow. G4 0NG<br>> _______________________________________________<br>> gpfsug-discuss mailing list<br>> gpfsug-discuss at spectrumscale.org<br>> <a href="https://urldefense.proofpoint.com/v2/url?" target="_blank" >https://urldefense.proofpoint.com/v2/url?</a><br>><br>u=http-3A__gpfsug.org_mailman_listinfo_gpfsug-2Ddiscuss&d=DwIGaQ&c=jf_iaSHvJObTbx-<br>> siA1ZOg&r=RGTETs2tk0Kz_VOpznDVDkqChhnfLapOTkxLvgmR2-<br>> M&m=Mr4A8ROO2t7qFYTfTRM_LoPLllETw72h51FK07dye7Q&s=z6yRHIKsH-<br>> IaOjtto4ZyUjFFe0vTGhqzYUiM23rEShg&e=<br>><br><br><br>_______________________________________________<br>gpfsug-discuss mailing list<br>gpfsug-discuss at spectrumscale.org<br><a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__gpfsug.org_mailman_listinfo_gpfsug-2Ddiscuss&d=DwIFAw&c=jf_iaSHvJObTbx-siA1ZOg&r=1mZ896psa5caYzBeaugTlc7TtRejJp3uvKYxas3S7Xc&m=whXeCPYkxzk5dnbnp3D-9cD3VasUhW-VIdocU6J7CuY&s=2QoNTGiUmBkQ_UhARaVpqet7Uo1lF15oAg6qNBiJPIQ&e=" target="_blank" >https://urldefense.proofpoint.com/v2/url?u=http-3A__gpfsug.org_mailman_listinfo_gpfsug-2Ddiscuss&d=DwIFAw&c=jf_iaSHvJObTbx-siA1ZOg&r=1mZ896psa5caYzBeaugTlc7TtRejJp3uvKYxas3S7Xc&m=whXeCPYkxzk5dnbnp3D-9cD3VasUhW-VIdocU6J7CuY&s=2QoNTGiUmBkQ_UhARaVpqet7Uo1lF15oAg6qNBiJPIQ&e=</a> </font><br> </div></blockquote>
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