Best Way to Layout Disks

[pcradduck]

I have 8 x 1TB disks, I have played with this in VMware and I am now ready to bring this to life. What is the best performance and redundancy mix, I am doing ZFS

1. RAIDZ2, allows 2 disk failures seems to be fast enough at least in VMware I get 30-35MBs (5.8TB of storage)

2. zpool with 4 mirror arrays in it, I seems to get a little speed bump 35-40MBs. That could just be VMware and the fact that all my VMDKs are on the same LUN so I only see marginal speed increase (3.4 TB of Storage) seems to allow 4 drive failures, as long as both drives in a single mirror don't fail at the same time.

Also a second question, why when I setup a ZFS mirror with 8 x 1 TB disk does it make a 1TB share with 7 disk failure capacity instead of making a ~3.4TB share with 4 disk failure capacity? Do I really have to keep making 2 disk mirrors and adding them to the pool to get to option #2?

Last and least important question, does ZFS stripe in FreeNAS allow you to fail 1 drives out, it seemed like in my testing in VMware it did?

Thanks for the help.

HARDWARE SPECS:
FreeNAS 8.0.1 x64
6GB PC2-6400
Core 2 Duo, 2.0GHz
2 Promise 4 Port SATA adapters.

 

[Durkatlon]

Yeah, if you want a stripe of mirrors and you want to set it up from the GUI, you'll have to create 4 separate 2-drive-mirrors and add them to the same volume. From the command line you can do it with a single "zpool create" and then "zpool export" followed by an import from the GUI. You won't get any swap on the drives if you go the command line route.

If you do a pure stripe (of single disks, not mirrors) you cannot lose any disk without the array degrading. If it appears the array is fine after a drive removal just try accessing the files on it. FreeNAS being slow to detect a zpool failure is a known bug.

Given you have 8 disks, I would go with a RAIDZ2 in your case. You only lose 2 drives to parity and you can afford to lose any combination of 2 drives. With the stripe-of-mirrors you can theoretically lose 4 drives if just the right ones fail, but if the wrong 2 fail you've already lost the entire volume.

 

[pcradduck]

Swap

Thanks.

So if I go command line where will the swap go vs GUI?

RAIDZ2 wont hurt my performance too much over a 4 mirror pool?

 

[Durkatlon]

If you do the zpool creation from the command line there'll be no swap. Honestly, in retrospect I wish I had done this, because I suspect that some of the disk replacement problems that people are having might be related to the fact that ZFS is not getting the entire disk when you create the pool from the GUI.

The striped mirror will have somewhat better performance but I doubt you'll notice it much.

 

[pcradduck]

OK, thanks for the advice, what is the command if i do it from command line? i did google, but I want to make sure the command is the same in Freenas as it is in Solaris.

Is it something like:
zpool create myzfs raidz2 /disk1 /disk2 /disk3 /disk4 /disk5 /disk6 /disk7 /disk8

 

[Durkatlon]

Yeah, that's it. Although with a RAIDZ2 you can create it from the GUI in a single step as well and I believe you can now (with recent builds) set swap to 0.

 

[pcradduck]

ok, what does FreeNas call each hard is it just da1 da2 da3...etc??

Sorry for the Noob question, not a ton of FreeNas CLI experience

 

[Durkatlon]

The answer is (you probably expected this), "it depends". I think if the SATA controller is in IDE mode the disks will be named da1, da2 etc, but if it's in AHCI mode it will be ada1, ada2 etc. Your best bet is to type "dmesg | less" at the command line and see under what names the devices are detected during boot-up.