We've got Debian Wheezy host with ZFS on Linux with in.
It is used only for serving large files over http.
User activity is mostly characterized by a lot of random read.
We've noticed that ~95% ARC hit rate
gives us ~80 MByte/s hdd reading activity
with the overall ~160 MByte/s server output.
I've already checked ARC and L2 prefetch options are disabled.
Linux read ahead for this array is set at default 512 and changing this value doesn't give any sensible effect.
What is the reason of such difference and is there any way to get proper statistic for real ARC usage?
