[gpfsug-discuss] QoS question

[Buterbaugh, Kevin L]

Hi All,

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:


"The IOPS values that you set in an mmchqos 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.

For example, if you 600 IOPS to the maintenance class, and there are six nodes that have the file system mounted, then QoS allocates 100 IOPS to the maintenance 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 maintenanceclass. "

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...

7,000 IOPs / 700 nodes would be 10 IOPs per node.

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.

466.67 * 700 (nodes in cluster) = 326,666.67.  So I would allocate 326,666 IOPs to the maintenance class?

Thanks in advance…

Kevin
—
Kevin Buterbaugh - Senior System Administrator
Vanderbilt University - Advanced Computing Center for Research and Education
Kevin.Buterbaugh at vanderbilt.edu<mailto:Kevin.Buterbaugh at vanderbilt.edu> - (615)875-9633



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://gpfsug.org/pipermail/gpfsug-discuss_gpfsug.org/attachments/20160614/e6f88339/attachment.htm>