Optimal Configuration?

[tastyhouse]

I have 5 3TB and 5 2TB drives (10 total) which I'd like to use to create a single share for my home network. I am running Freenas 9.2. When I attempted to create a single volume from all the drives During the creation of the volume freenas had me configure 2 volumes (15TB and 10TB) each in a RaidZ configuration. Afterwards the single volume was created successfully at approximately 18TB.

I'm trying to understand exactly how this volume is set up. I THINK there are two separate zfs pools - the 15TB in a raidz and the 10TB in a raidz - and freenas is striping between the two to create the one volume of 18TB. Can somebody please confirm that for me? I would assume if a drive fails the entire volume would be unavailable until that drive was replaced. I just want to make sure i'm not at severe risk of losing all my data in this configuration.

I'm sorry if this has been asked before but I did search the forums for something similar and had a difficult time finding it.

 

[tastyhouse]

Okay so I think this might be it from the volume section of the freenas manual :
When adding disks to increase the capacity of a volume, ZFS supports the addition of virtual devices, known as vdevs, to an existing ZFS pool. A vdev can be a single disk, a stripe, a mirror, a RAIDZ1, RAIDZ2, or a RAIDZ3. Once a vdev is created, you can not add more drives to that vdev; however, you can stripe a new vdev (and its disks) with the same type of existing vdev in order to increase the overall size of the ZFS pool. In other words, when you extend a ZFS volume, you are really striping similar vdevs.

Basically a raidz1+0 config.

 

[SmallGuy]

Read or read again this: http://forums.freenas.org/threads/slideshow-explaining-vdev-zpool-zil-and-l2arc-for-noobs.7775/
Yes both vdev are striped together to form one pool.
Assuming you have done two RAIDZ1 vdev, If you loose one drive, your pool isn't unavailable but is in a degraded state until you replace the defective drive.
The risk with RAIDZ1 is to loose another drive on the same vdev during the re-silvering of one drive, and consequently loose the vdev. This risk increase with the size of the drives as the re-silvering is more longer, and with the number of drive per vdev. If you loose one vdev all your pool is trashed.
RAIDZ2 is safer for this reason.
Bottom line, 5 drives aren't optimal in RAIDZ2 configuration for performance reasons.

So, this set-up is perhaps optimal regarding the hardware that you own, but not optimal in general (to my eyes).

 

[gpsguy]

I *thought* I replied to you last night. Anyway, while non-optimal, you could create a 10 disk RAIDz2 volume, by doing the installation with FreeNAS 8.3x (http://cdn.freenas.org/). You'll have less disk storage (~14Gb), but have more protection.

The array will be based on the size of the smallest disks (2Tb). If you were to replace the 2Tb drives with 3Tb drives, once all 5 had been replaced, your storage would expand and be based on the 3Tb drives.\

The ability to mix drive sizes was available in 8.x, but the feature was removed in v9. So, you could create the pool with v8.3 and then immediately upgrade to v9.2.