PerfStat is a great way to get some quite detailed performance information out of the filer when you have a performance or other issue that you can’t quite put your finger on. You need to have access to the PerfStat Viewer, or get someone to process this output for you, and then you need to trawl through it.

Operations Manager, and more specifically Performance Advisor is brilliant and 99% of the time gives you the counters you need to diagnose the problem. Once you’ve found your way round it, it is completely indispensible!

But what if you don’t have Operations Manager, or you just want to quickly pull out information on one area of the system?

First things you want to look at sysstat. Everyone’s best friend and great way of seeing “Is my system busy?”. Whenever you run sysstat, make sure to through it the “-s” modifier so that you get a summary at the end of the output. If you don’t define a number of iterations (-c <num>), then ctrl+c to break the output. “-x” is great for giving all areas of output, but it can be a little wide sometimes. “-u” is my favourite as it gives you utilisation readings and these the usually the most useful when troubleshooting.

Most of the columns are fairly self explanatory. CPU is % busy, NFS, CIFS, HTTP, FCP and iSCSI are all protocol operations counters. Net kB/s in and out are obvious (for reference a single gigabit interface will happily sustain around 80MB/s, but can stretch to 110/120MB/s). Disk and Tape in&out. Watch the cache age when it gets really low, but there’s better counters for that. Cache hit is a counter you want as close to 100% as possible. The more data is getting read from cache the better! CP Type is Consistency Points, I won’t go into detail as to what these are, there is a very good KB article on this already (https://now.netapp.com/Knowledgebase/solutionarea.asp?id=kb23471). And finally Disk Utilisation which seems to cause some confusion. This is the reading from the single busiest disk in the system, and not an average. This reading can interestingly go about 100% (much like CPU can too), and this simply means the disks are doing more than they should!  Read more... (1670 words, estimated 6:41 mins reading time)