ZFS ZFS & memory: 30G wired, only 3796K Active?

[grep2grok]

So, I had 4 GB in this machine I set up as a ZFS pool (three 2x mirrors of 6 6TB SATA drives) serving an iSCSI target. I kept eyeing top and it's pretty well stuck at 3700M active and 40M free. I'm transferring 12TB of mission critical data, probably don't want memory to be the choke point, so after a couple days I decided to pause the transfer at the app server and install 32GB of RAM in the ZFS machine.

Welp, now I've got 30G wired and 40M free. But only 3768M active.

I'm not using deduplication. No real change in performance.

Is the kernel *really* using 30G?

 

[robroy]

grep2grok, that wired space is being used for the ZFS ARC, and it's normal.

If you'd like to reduce the amount of memory used for this, add something like vfs.zfs.arc_max="8192M" to /boot/loader.conf. I heard about this on BSD Now.