ZFS on Linux: How to find the arc stats (was arcstat.py)

This has now changed; run the following to find the adaptive read cache stats (ARC):  
cat /proc/spl/kstat/zfs/arcstats
  You can gleam some really useful information out of how your RAM is being utilised and what your required ARC size might be from the results – this may be a topic for a future post, however!

ZFS on Linux (Ubuntu) – arcstat.py is now available! How do you run it?

UPDATE: This information is now out of date, see new post https://www.sotechdesign.com.au/speed-dating-bucks-county-pa/.   One very handy ZFS-related command which has been missing from the standard ZFS on Linux implementation has been arcstat.py. This script provides a great deal of useful information about how effective your adaptive read cache (ARC) is.   ZFSoL 0.6.2 includes it, which you can now update to in Ubuntu with apt-get upgrade. But how do you actually use it when you upgrade? Easy. Assuming you have python installed, run the following (this works for 13.04 at least – we will check the others and update when we do):  
  This will provide you with the default readout, e.g. for our system which just rebooted:  
    time  read  miss  miss%  dmis  dm%  pmis  pm%  mmis  mm%  arcsz     c 21:33:13     3     1         33          1       33        0        0           1        33       2.5G   15G
  As you can see, since the system has just rebooted and hasn’t started caching requests the ARC size is quite small – 2.5G. This is an extremely useful tool to get an idea of how your ARC is performing – we will do a piece on interpreting the results soon!