VSAN-Troubleshooting-Reference-Manual

Diagnostics and Troubleshooting Reference Manual – Virtual SAN
Using RVC for performance monitoring
There are some RVC commands that can give administrators an overview of Virtual
SAN performance. Here is one such command.
vsan.vm_perf_stats
vsan.vm_perf_stats ~/vms/W2k12-SQL2k12 --interval 10 --show-objects
output:
2014-10-31 15:19:33 +0000: Got all data, computing table
+--------------------------+-------------+--------------+--------------+
| VM/Object | IOPS | Tput (KB/s) | Latency (ms) |
+--------------------------+-------------+--------------+--------------+
| W2k12-SQL2k12 | | | |
| /W2k12-SQL2k12.vmx | 0.3r/0.3w | 0.2r/0.2w | 0.5r/1.2w |
| /W2k12-SQL2k12.vmdk | 1.2r/6.1w | 7.7r/46.5w | 0.4r/1.8w |
| /W2k12-SQL2k12_1.vmdk | 0.0r/7.7w | 0.4r/1236.7w | 0.8r/1.8w |
| /W2k12-SQL2k12_2.vmdk | 0.4r/647.6w | 1.6r/4603.3w | 1.3r/1.8w |
+--------------------------+-------------+--------------+--------------+
By way of understanding the relationship between the metrics, the following
calculations may help:
IOPS = (MBps Throughput / KB per IO) * 1024
MBps = (IOPS * KB per IO) / 1024
Using VSAN Observer for Performance Monitoring
One should take the time to familiarize oneself with VSAN Observer, even when
there are no anomalies occurring on the Virtual SAN cluster. Check what is a normal
value for metrics like latency, IOPS, Outstanding IO, bandwidth, etc. It may even be
worth gathering offline bundles from time to time to use as reference against
possible future issues.
As mentioned in the VSAN Observer section, any metrics that exceed boundary
thresholds will be displayed with a red underline against the chart. This can then be
used as a point to start investigating the root cause. Various reasons why some of
these charts may be outside their respective thresholds have been discussed, but
anything from an overloaded system to poor performing devices to physical switch
issues impacting the network could be a root cause. Fortunately, VSAN Observer can
assist with all of this.
Next some VSAN Observer case studies are examined, where there are details on
what to expect from VSAN Observer when some common scenarios are encountered.
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