OpenZFS on OS X

Hi Brendon,

I've been reading various sites about performance tuning (many are by you I guess) while trying to get my head around ARC, etc. I am a near zfs novice trying to understand what is going on with this zfs system so please bear with my questions if they seem stupid!

The attachment shows the stats for a core i7 MacMini with 16 GB of RAM with 10.11.4 running the 1.4.5 kexts and two 4-disk RAIDz disk arrays (one backs up the other) on external USB3. The main HDD is running nothing else but the system. It is not heavily used and basically is for archiving about 6 TB of data with may be a few dozen file changes each day. The emphasis is on keeping a stable secure archive rather than fast I/O.

Do you think these stats fall into the normal ballpark given this background—especially the 0 result for sysctl kstat | grep arc_max.

Looks normal for an extremely idle machine.

The tunable sysctls are write only, meaning that they are set via:

Code: Select all

sudo sysctl -w kstat.zfs.darwin.tunable.zfs_arc_max=<whatever in bytes>


but read like:

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sysctl kstat.zfs.darwin.tunable.zfs_arc_max
kstat.zfs.darwin.tunable.zfs_arc_max: 0


When these tunables are written to the outcome is reflected elsewhere, in this case the sysctl named kstat.zfs.misc.arcstats.c_max IIRC. While this may seem counterintuitive, the tunable sysctls are really emulating a completely different configuration mechanism from Solaris/Illumos.

Cheers
Brendon

Thanks Brendon.

Hi Brendon,

Could we chat in IRC. I have many Finder hangs on this setup and within the hang reports there are references to zfs. They probably mean nothing but I need some guru advice .

Thanks.