QoS on file level (cinder - ontap/NFS)

[iamsam]

Hello

I have cinder pools are backed by ontap NFS exports.
QoS on Cinder volumes is set by Openstack as per :
https://docs.openstack.org/cinder/queens/configuration/block-storage/drivers/netapp-volume-driver.html

The QoS is working fine. Although sometimes the throughput exceeds the limit for few seconds before returning back to normal. I found that during those times the IOPS was too high(> 5000 iops) compared to normal(~ 100).  

So, I assume I need to set the proper IOPS, so that volumes not exceed the throughput ceiling.
But I cannot figure out how to calculate this proper IOPS value!
Say, for 100MB/sec maximum throughput, what is the maximum IOPS value I need to set ?

Table below is a sample output of "qos statistics workload performance" command
As you see, for the same IOPS value the throughput is not the same.

[paul_stejskal]

You can set a QoS ceiling policy to either IOPS, bytes/sec, or both. Why not just set it to 100 MB/s or "100iops,100MB/s"?

[iamsam]

Hi Paul, thanks for comment.
With the throughput limit only set, I can see some clients can exceed the limit(for few seconds). During this, I see they are pushing high IOPS. I noticed that when I add IOPS limit in the policy-group, the throughput is not exceeding the limit much like before.

[paul_stejskal]

I'm glad that helped.