OpenZFS on OS X

I'm keen on upping my Mac mini server storage and I have looked at the owc thunderbay mini with 4*2tb drives.
I do have the Mac mini server 2012 model with dual 256ssd and wanted to put one as a cache for the external raid. (Thinking raidz).
Would I gain much from doing this? I use it for backup and plex storage at the moment.
How much ram would be required to handle 8tb raidz + 256gb ssd cache?

Any caveats I should consider first? Or is it as easy as I am hoping?

For streaming loads I doubt that you will see any significant benefit from the cache. Your usage sounds a little like mine, I have an uncached tbolt raidz2 serving home directories, backups, music and video around my house on a wired LAN. No particular performance issues.

Brendon

glemme wrote:I'm keen on upping my Mac mini server storage and I have looked at the owc thunderbay mini with 4*2tb drives.
I do have the Mac mini server 2012 model with dual 256ssd and wanted to put one as a cache for the external raid. (Thinking raidz).
Would I gain much from doing this? I use it for backup and plex storage at the moment.
How much ram would be required to handle 8tb raidz + 256gb ssd cache?

Any caveats I should consider first? Or is it as easy as I am hoping?

Ok, the internal SSD was most for fun. if it won't add anything I might skip it. (I thought it would add some performance but if not I can use it as a cache folder for my system)

But on to the ram requirements. I read that ZFS uses a lot of ram. 1gb / 1TB. so with a 8TB raid (6TB usable space) I should aim for 6-8 GB ram for just doing the filesystem? or should I use more? I think the limit in my mini is 16GB so that is half the memory just for the filesystem?

Thanks for clarification.

With respect to RAM, its really up to you. Less RAM ~= less performance, more ~= More performance. Most of the memory is used for caching (ARC). You can tune it up and down to taste.

For home use and in particular streaming, you wont need 8GB of RAM IMO, although it would use it.

I should also add that if you leave o3x in its default configuration, it will utilise nearly all of your computers memory, until such time as the machine experiences memory pressure e.g. a new application is opened. At which point o3x will release memory in accordance with the load. This mechanism is not 100% perfect, but is generally good enough.

Some people cant get over the idea that ZFS is using most of the computers memory, however in many ways its not really different from the OS filesystem cache. If you look at the memory usage graph, we show up as "wired" memory, whereas the OS cache does not feature on the graph itself.

Brendon

I'm a relative newbie when it comes to RAID. I'm refreshing my home system based around a new mac-mini w/ 256 GB SSD and thinking an OWC Thunderbay 4 12TB RAID 1. I would like to implement ZFS on the TB4 for the obvious data integrity aspect (irreplaceable home video of relatives now gone, kids grown up, etc). Has anyone had success with this? I asked Macsales tech support and they reported it couldn't be done but based on this thread it sounds like that isn't right. Could anyone confirm before I plunk down my hard-earned?
Thanks,
Greg

Just make sure your storage case can present the disks in JBOD (Just a Bunch Of Disks), then you can ZFS without issues. If it only does various types of RAID/mirror/stripe without JBOD, then it can not just let ZFS handle it. You can still using it, but it'd be a hardware raid with ZFS on top, which isn't what you want.

I use a Lacie 5BIG, it is ONLY a JBOD, and works fine. Pretty sure the Promise units can do JBOD, you need to check the devices specs.

lundman wrote:Just make sure your storage case can present the disks in JBOD (Just a Bunch Of Disks), then you can ZFS without issues. If it only does various types of RAID/mirror/stripe without JBOD, then it can not just let ZFS handle it. You can still using it, but it'd be a hardware raid with ZFS on top, which isn't what you want.

Thanks that's just what I thought. It’s a S/W RAID (JBOD, even labeled as such) so tech was wrong. Many Thanks!