Thursday, August 6, 2015

CDOT Tip #11: Performance on the Fly (QOS)

QOS is the performance management system within ONTAP.  It doesn’t just stop a volume from going above a certain level of performance, it also monitors and manages performance.  So it’s your one-stop shop for most perf questions!

You can use ‘qos statistics latency show’  to see volume-level latency numbers.   
-          The left most column ‘Latency’ is total latency from request received until response to the client
-           ‘Network’ is the time it takes to traverse the network stack inside ONTAP
-          ‘Cluster’ will show latency due to indirect IO
-          ‘Data’ is ONTAP itself
-          ‘Disk’ is time to leave the controller and hit the disk
cluster1::> qos statistics latency show -iterations 100 -rows 3
Policy Group           Latency    Network    Cluster    Data       Disk       QoS
-------------------- ---------- ---------- ---------- ---------- ---------- ----------
-total-                110.35ms   110.02ms        0ms   327.00us        0ms        0ms
vs1vol0                167.82ms   167.22ms        0ms   603.00us        0ms        0ms
vol1                   117.76ms   117.56ms        0ms   191.00us        0ms        0ms
vol2                    44.24ms    44.05ms        0ms   190.00us        0ms        0ms
-total-                 38.89ms    38.63ms        0ms   256.00us        0ms        0ms
vol2                    64.47ms    64.20ms        0ms   266.00us        0ms        0ms
vol1                    27.28ms    27.03ms        0ms   253.00us        0ms        0ms
vs1vol0                 23.72ms    23.47ms        0ms   249.00us        0ms        0ms
-total-                409.81ms   409.65ms        0ms   169.00us        0ms        0ms

A simpler view with IOPS and throughput can be found using qos statistics performance show.’
    cluster1::> qos statistics performance show -iterations 100 -rows 4
Policy Group           IOPS      Throughput   Latency
-------------------- -------- --------------- ----------
-total-                    79     1296.00KB/s   337.41ms
_System-Best-Effort        25           0KB/s        0ms
vol1                       24       96.00KB/s   193.72ms
vol2                       18     1152.00KB/s   750.98ms
vs1vol0                    12       48.00KB/s   707.38ms
-total-                   109        1.99MB/s   133.27ms

Please note that the –total- line indicates the system-wide performance.  Very useful!