Need advice on different sized drives

[gillycheesesteak]

Hello,

I'm new to FreeNAS, but I'd like to set up a server with it in my home with what I have and can get cheap/free, so I'm looking for some advice on whether this is possible and/or advised.

What I have currently is 5 drives:
2x 1TB
2x 2TB
1x 3TB

I've looked around a lot and I think I've come to understand what I can and can't do, but I wanted to ask anyway to make sure. I want to combine these drives in the way that protects my data but gives me the largest possible usable capacity. My initial thought was to somehow combine each 1TB drive with a 2TB in a RAID 0 format, and then do a RAID-Z across 3x3TB (6TB usable capacity). Another thought in the same thread was to combine the 1TB drives together, and RAID-Z across all 4 "drives", which would waste 1TB on the 3TB drive, but again give me 6TB usable capacity. From my reading it does not seem that this is possible, but if it is, I would like to hear about how to do it.

My other idea that seemed doable, but that it seems to me is inadvisable, would be to create two separate vdevs: the 2TB drives and the 3TB drive in a RAID-Z, and then mirror the 1TB drives on each other, giving me a total of 5TB usable capacity (not as good, but acceptable).

Any thoughts?

 

[Caesar]

I don' t think you can raid0 a 1TB with a 2TB and then have act as a 3TB drive for 3x3TB Raid-Z. I think your best bet would be to do the two vdevs with vdev1 = [2x2TB + 1x3TB] RAID-Z and vdev2 = 2x1TB Mirrored. Then you can expand vdev1 with 3x3TB and take those 2x2TB and expand vdev2. That should give you around 8TB whenever you can afford getting two more 3TB drives.

I assume you are aware that the docs say that you should not mix raid types in the same pool?

 

[gillycheesesteak]

I don't have any experience with RAID, but here's what I thought might work: If I got a hardware RAID controller, and used that for the two 1TB drives, and configured them as a RAID0, would that allow FreeNAS to see them as 1 drive? I'm just throwing out ideas here, because I think this would be the best solution if it were possible. Should one of the 1TB drives fail, I could get a new 2TB and resilver onto that, if my thinking is correct.

As for your question, I read somewhere that mixing RAID types was not recommended, but I never discovered why that was.

 

[Caesar]

well your not suppose to use a hardware raid with zfs because you will lose most of the benefits of zfs as for the mixing of raid types I think it has something to do with performance but I am not sure why they say not to do it.

 

[cyberjock]

You can't do what you want to do. If you don't use the same size disk in the same vdev you will lose all space on all drives that is bigger than the smallest disk. Not to mention Caesar is right that you shouldn't be mixing hardware RAID and ZFS at all.

As for mixing and matching, its for a bunch of reasons but there is no way to mitigate it so just go with it. I explained it in extreme detail months ago and I don't have time to explain it again today.