ZFS Raid Options

[BigBadBooey]

Hi,

I am now setting up FreeNAS 9.1 and have a RAID question to ask please. I am assuming that ZFS is the better option.

My server is HP DL380 G8, 32Gb RAM, 1 Process (2.2Ghz), 4 x 1Gb Network card, 8 x 600Gb 15k HDD, 2Gb CACHE P420i Card

I currently have created 8 x RAID 0 Disks using the HP SmaryArray manager so that the disks are presented individually to FreeNAS - this it sees (da0 through to da7).

Previously if I had the SmartArray performing hardware RAID (all drives in RAID 5) then I had 4.2Tb presented as a single disk to FreeNAS. Setting up a ZFS Stripe gave me a 3.8TiB Volume and I had the benefit of HP SmartArray doing the RAID.

However, now, I have FreeNAS telling me the optimal setting is RaidZ2 giving me 2.18TiB of usable space which is really where I don't want to be.

So the question is, do you think its better to go for HP SmartArray RAID 5 and then ZFS Stripe - if I go for RaidZ then its 3.2TiB and FreeNAS tells me this is Not Optimal.

Confused? Me too :)

 

[StephenFry]

You're asking this question in a FreeNAS forum, I think you'll know what the answer is going to be :)

Few people like to use 8 large (2TB+) drives in a RAID5-type setting. With 600Gb drives, this might be less of a problem, but I personally still would prefer RAIDZ2, even with 8 drives. (6 or 10 would be preferable)

Just let FreeNAS and ZFS do the work. I'd forget about the HP's hardware capabilities if I were you. But maybe others here have a different opinion...

 

[PinkyThePig]

Hi,

I am now setting up FreeNAS 9.1 and have a RAID question to ask please. I am assuming that ZFS is the better option.

My server is HP DL380 G8, 32Gb RAM, 1 Process (2.2Ghz), 4 x 1Gb Network card, 8 x 600Gb 15k HDD, 2Gb CACHE P420i Card

I currently have created 8 x RAID 0 Disks using the HP SmaryArray manager so that the disks are presented individually to FreeNAS - this it sees (da0 through to da7).

Previously if I had the SmartArray performing hardware RAID (all drives in RAID 5) then I had 4.2Tb presented as a single disk to FreeNAS. Setting up a ZFS Stripe gave me a 3.8TiB Volume and I had the benefit of HP SmartArray doing the RAID.

However, now, I have FreeNAS telling me the optimal setting is RaidZ2 giving me 2.18TiB of usable space which is really where I don't want to be.

So the question is, do you think its better to go for HP SmartArray RAID 5 and then ZFS Stripe - if I go for RaidZ then its 3.2TiB and FreeNAS tells me this is Not Optimal.

Confused? Me too :)

Well a couple of things. The first scenario is a very very very bad idea. You are very likely to just lose your whole pool as well as be unable to do certain key features of ZFS. If choosing between your raid 50 and raid z1 please for the love of god choose z1. Having said that, Z2 is much preferred once you hit 6+ disks as lets take a scenario into account:

6 drives are cruising a long and bam one dies. You swap it out and the resilver process starts. This takes probably a day in your use case. During that day another hard drive, from the extra workload and the fact that it was built in the same conditions and was subject to the exact same usage amount as the first starts to die as well and is spitting out errors. In raid z1 you are completely screwed. in raid z2 you keep on cruising.

Ultimately whether you choose z1 or z2 depends on how much you care about the data you have. If its just an additional backup or replaceable media files then by all means go z1. But if you are storing family pictures or something else of a hard to replace nature then go z2. When hard drives start failing down the road you will thank yourself for z2.

Six hard drives is that right on the line case where you could potentially go a risky raid z1 setup or the raid z2.

EDIT: I just realized you have 8 drives, not 6. With 8 drives there is no way that you should be running raid 5/z1 as your chances of catastrophic failure is way high on that.