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Hi All,
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<div class="">We have recently upgraded to GPFS 4.2.0-3 and so I am getting ready to dive into my first attempts at using the new QoS features. I want to make sure I am understanding the documentation:</div>
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<p class=""><span style="font-size: 10.000000pt; font-family: 'Palatino'" class="">"The IOPS values that you set in an
</span><span style="font-size: 10.000000pt; font-family: 'Palatino'; font-weight: 700" class="">mmchqos
</span><span style="font-size: 10.000000pt; font-family: 'Palatino'" class="">command apply to all I/O operations that are issued by all the nodes that have the specified file system mounted. You should adjust your allocations of IOPS accordingly.
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<p class=""><span style="font-size: 10.000000pt; font-family: 'Palatino'" class="">For example, if you 600 IOPS to the
</span><span style="font-size: 10.000000pt; font-family: 'Palatino'; font-weight: 700" class="">maintenance
</span><span style="font-size: 10.000000pt; font-family: 'Palatino'" class="">class, and there are six nodes that have the file system mounted, then QoS allocates 100 IOPS to the
</span><span style="font-size: 10.000000pt; font-family: 'Palatino'; font-weight: 700" class="">maintenance
</span><span style="font-size: 10.000000pt; font-family: 'Palatino'" class="">class of each node. If you then run maintenance commands that affect only three of the nodes, the commands runs with an actual allocation of 300 IOPS, or 100 IOPS per node. To run
maintenance commands that affect three nodes with an actual allotment of 600 IOPS, or 200 per node, allocate 1200 IOPS to the
</span><span style="font-size: 10.000000pt; font-family: 'Palatino'; font-weight: 700" class="">maintenance</span><span style="font-size: 10.000000pt; font-family: 'Palatino'" class="">class. "</span></p>
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<div class="">We have a ~700 node cluster with 15 NSD servers. Here’s how I interpret the above assuming that I have determined that I want to allow 7,000 IOPs … please correct me if I’m wrong...</div>
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<div class="">7,000 IOPs / 700 nodes would be 10 IOPs per node.</div>
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<div class="">But I want those 7,000 IOPs to be divided amongst my 15 NSD servers that are going to be doing the maintenance (a restripe, for example), so 7,000 / 15 = 466.67.</div>
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<div class="">466.67 * 700 (nodes in cluster) = 326,666.67. So I would allocate 326,666 IOPs to the maintenance class?</div>
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<div class="">Thanks in advance…</div>
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<div class="">Kevin</div>
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<div class="">—</div>
<div class="">Kevin Buterbaugh - Senior System Administrator</div>
<div class="">Vanderbilt University - Advanced Computing Center for Research and Education</div>
<div class=""><a href="mailto:Kevin.Buterbaugh@vanderbilt.edu" class="">Kevin.Buterbaugh@vanderbilt.edu</a> - (615)875-9633</div>
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