<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">What does iostat output look like when you’re running the tests on GPFS? It would be good to confirm that GPFS is successfully submitting 2MB I/o requests. <div><br id="lineBreakAtBeginningOfSignature"><div dir="ltr">Sent from my iPhone</div><div dir="ltr"><br><blockquote type="cite">On Feb 7, 2024, at 08:08, Michal Hruška <Michal.Hruska@mcomputers.cz> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr">
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<p class="MsoNormal">Dear gpfsUserGroup,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">we are dealing with new gpfs cluster (Storage Scale 5.1.9 – RHEL 9.3) [3 FE servers and one storage system] and some performance issues.<o:p></o:p></p>
<p class="MsoNormal">We were able to tune underlying storage system to get to performance ~4500 MiB/s from 8 RAID groups using XFS (one XFS per one RAID group) and parallel fio test.<o:p></o:p></p>
<p class="MsoNormal">Once we installed the gpfs – one FS accross all 8 RAID groups and we observed performance drop down to ~3300 MiB/s using the same fio test.<o:p></o:p></p>
<p class="MsoNormal">All tests were performed from one front-end node connected directly to the storage system via FibreChannel (4 paths each path is 32GFC).
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Storage systems RAID groups are sized to fit 2MB data blocks to utilize full-stripe writes as the RAID geometry is 8+2 using 256KB block size -> 8*256KB = 2MB.<o:p></o:p></p>
<p class="MsoNormal">I/O pattern on FC is optimized too.<o:p></o:p></p>
<p class="MsoNormal">GPFS metadata were moved to NVMe SSDs on different storage system.<o:p></o:p></p>
<p class="MsoNormal">We already tried some obvious troubleshooting on gpfs side like: maxMBpS, scatter/cluster, different block sizes and some other parameters but there is no performance gain.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We were advised that gpfs might not perform pure sequential writes towards the storage system and therefore the storage system is performing more random I/O than sequential.
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Could you please share with us some thougths about how to make gpfs as much sequential as possible? The goal is to reach at least 4000 MiB/s for sequential writes/reads.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Tahoma",sans-serif;mso-fareast-language:CS">best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:12.0pt;font-family:"Tahoma",sans-serif;color:#DC261E;mso-fareast-language:CS">Michal Hruška</span></b><span style="font-size:12.0pt;font-family:"Tahoma",sans-serif;color:#DC261E;mso-fareast-language:CS"><o:p></o:p></span></p>
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