I've been using zfsonlinux on my server for what seems like ages now, and when I discovered lately that TimeMachine didn't consider a completely reformatted and repopulated 100GB image file as having changed, and thus not backing it up, I started to think about alternatives. What comes to mind immediately is of course ZFS, and so I was immensely happy to see that ZEVO was no longer the only feasible option. OpenZFS on OS X had appeared! Very beautiful.
One thing, though, that I'm having a bit of trouble with, is the performance of it. (Also a few lock ups that force me to hard reset my laptop, but let's not go there right now).
Since I'm using it for backup, and I'm backing up to an external USB2 drive, I've opted for gzip-9 compression, since it's slow, yes, but more efficient than any other current compression option, and the USB2 bottleneck would theoretically trump my CPU bottleneck — this is a MacBook Air 2013, i7, 8GB RAM, 500 GB SSD.
Okay, so here's the deal. I'm doing my backups with rsync. Specifically,
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nice sudo rsync -avxc --delete --exclude-from=/Users/daniel/.rsync-backup-exclusions / /Backup/Air/
I added the nice part to alleviate the problem, but it doesn't seem to help. The problem is beachballs galore, and massive system lockups (nothing responding for up to 30 seconds) while running this. It seems to get worse over time (memory related?), and particularly bad when backing up large files (such as VMware disk files).
It seems also that it may bring ZFS into some sort of funk, as twice I've tried unmounting and ejecting my ZFS USB drive to sort of "clean the slate", and ended up with hanging zpool and zfs commands until a reboot (which may or may not have required hard rebooting).
Any ideas about this?
Oh, btw, I'm on Yosemite beta, this might very well be very relevant!
EDIT: This does seem very much related to writes rather than reads. I'm currently doing -avxc rsync over an existing backup, which means reading the entire ZFS data before writing anything, and while UI performance is definitely suffering (much more than expected), I see no beachballs, and no lockups per se. Only lagging text input and slow screen updates. And, of course, the fan noise