RAID Question

[drwoodcomb]

I wasn't to build a freenas server and I was given 8 new hard drives that are pretty awesome so I would rather not have to buy anymore to add to the ones I just got.

2 x 1TB WD Se
2 x 2TB WD Se
2 x 3TB WD Se
2 x 4TB WD Se

I am not sure what RAID to use for this. Originally I was thinking RAID 10 but Im not sure if that would work.

(1TB+2TB+3TB+4TB) mirrored to (1TB+2TB+3TB+4TB) but I am not sure if that would work because I don't think striping can work between several different sized drives without the striped set defaulting to the lowest capacity drive in the set. Would I just be better off having 4 different sets of RAID0 for each pair of hard drives?

 

[MrToddsFriends]

(1TB+2TB+3TB+4TB) mirrored to (1TB+2TB+3TB+4TB) but I am not sure if that would work because I don't think striping can work between several different sized drives without the striped set defaulting to the lowest capacity drive in the set. Would I just be better off having 4 different sets of RAID0 for each pair of hard drives?

In ZFS a pool consists of one or more vdevs where a vdev consists of one or more disks. Mirroring can be done at vdev level. If you create a pool consisting of several mirror vdevs you essentially have striped mirrors. The other way around, striping several disks in a vdev and mirroring these vdevs at pool level (would be "mirrored stripes"), isn't possible in ZFS (at least: to my knowledge).

https://forums.freenas.org/index.php?threads/comprehensive-diagram-of-the-zfs-structure.38865/

Other good reads for starters:

https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/
https://forums.freenas.org/index.php?threads/terminology-and-abbreviations-primer.28174/

 

[Spearfoot]

Originally I was thinking RAID 10 but Im not sure if that would work.
(1TB+2TB+3TB+4TB) mirrored to (1TB+2TB+3TB+4TB) but I am not sure if that would work because I don't think striping can work between several different sized drives without the striped set defaulting to the lowest capacity drive in the set. Would I just be better off having 4 different sets of RAID0 for each pair of hard drives?

Perhaps you're thinking of RAIDZ1/2/3 vdevs, where you do lose the space on any disks larger than the smallest disk in the vdev. But the vdevs making up a pool don't have to be the same size. So you can stripe vdevs of any type (RAIDZ1/2/3 or mirrors) adding the full capacity of each vdev to the pool. I believe you're on the right track with mirrors.

I would create a single pool of 4 striped vdevs, each a mirrored pair of identically-sized drives:

• vdev0: 2 x 1TB
• vdev1: 2 x 2TB
• vdev2: 2 x 3TB
• vdev3: 2 x 4TB

In your case, this will give you ~10TB of storage space -- 1+2+3+4TB -- less some overhead, of course.

I tried this just now with my 'sandbox' FreeNAS installation running on VirtualBox. I found it was easier to use Manual Setup to create the pool (named 'tank') with da0 and da1 in a mirror. Then I used Manual Setup to extend 'tank' three times, adding da2+da3, da4+da5, and da56+da7 as the 2nd, 3rd, and 4th vdevs. It's a lot harder to write than it is to do; these screenshots may clarify the procedure and the result:

 

[MrToddsFriends]

And don't forget to test all your HDDs thoroughly before putting valuable data your server. Remember: In a striped mirror setup you have only one disk for redundancy in each vdev (2-way mirrors assumed). And a loss of a single vdev would leave the whole pool damaged.

https://forums.freenas.org/index.php?threads/how-to-hard-drive-burn-in-testing.21451/
https://forums.freenas.org/index.php?threads/building-burn-in-and-testing-your-freenas-system.17750/

 

[drwoodcomb]

Perhaps you're thinking of RAIDZ1/2/3 vdevs, where you do lose the space on any disks larger than the smallest disk in the vdev. But the vdevs making up a pool don't have to be the same size. So you can stripe vdevs of any type (RAIDZ1/2/3 or mirrors) adding the full capacity of each vdev to the pool. I believe you're on the right track with mirrors.

I would create a single pool of 4 striped vdevs, each a mirrored pair of identically-sized drives:

• vdev0: 2 x 1TB
• vdev1: 2 x 2TB
• vdev2: 2 x 3TB
• vdev3: 2 x 4TB

In your case, this will give you ~10TB of storage space -- 1+2+3+4TB -- less some overhead, of course.

I tried this just now with my 'sandbox' FreeNAS installation running on VirtualBox. I found it was easier to use Manual Setup to create the pool (named 'tank') with da0 and da1 in a mirror. Then I used Manual Setup to extend 'tank' three times, adding da2+da3, da4+da5, and da56+da7 as the 2nd, 3rd, and 4th vdevs. It's a lot harder to write than it is to do; these screenshots may clarify the procedure and the result:
View attachment 13868 View attachment 13869

I finally got my system built. Thanks for taking the time to test this out for me. I am going to try and set it up now. I was having trouble flashing a RAID card into IT mode which, come to think of it, I think it was you that helped me out with it in another thread.