ZFS Pool Question

[rdx321]

Guys, I currently have a mirrored zfs pool with 10 6tb hard drives. I want to take 5 of those drives and setup an identical freenas machine but without pool mirroring.

My questions is, if one of the hard drives in a non mirrored pool fails, do I loose the data from the entire pool, or just the data that was on that one failed hard drive?

 

[DrKK]

You have 5 vdevs in one pool, each of which is a mirrored pair of 6TB drives, that's what you're saying?

If that's correct, then yes, when if you were to pull out one drive from each vdev, then every vdev in your pool is without parity, and if any *ONE* of them goes, then the vdev will drop. If any vdev in a pool drops, then you lose all of the data in a pool.

You can show us the output to "zpool status" to make sure that my assumption of your pool layout is correct, because there could be some ambiguity in how you described it.

But in general, no matter what you mean, whatever you are saying sounds to me like once I understand it, it will be a "super, horrifically, stupid idea."

 

[rdx321]

This is the export of one of my current pools that is mirrored.

pool: tv
state: ONLINE
scan: resilvered 1.99M in 0h0m with 0 errors on Tue Jun 9 20:03:52 2015
config:

NAME STATE READ WRITE CKSUM
tv ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
gptid/91496b4f-8d30-11e4-baac-0cc47a097d84.eli ONLINE 0 0 0
gptid/91d651ac-8d30-11e4-baac-0cc47a097d84.eli ONLINE 0 0 0
mirror-1 ONLINE 0 0 0
gptid/4018876e-8de7-11e4-858d-0cc47a097d84.eli ONLINE 0 0 0
gptid/408fdea0-8de7-11e4-858d-0cc47a097d84.eli ONLINE 0 0 0
mirror-2 ONLINE 0 0 0
gptid/59c5b0fc-108e-11e5-85e2-0cc47a097d84.eli ONLINE 0 0 0
gptid/5a4d7a24-108e-11e5-85e2-0cc47a097d84.eli ONLINE 0 0 0


So if I un-mirror the TV pool, and keep just 3 hard drives, if one of those 3 hard drive fails, I loose the data in the entire pool?

 

[DrKK]

Right so, what you just showed me, was a zpool containing three vdevs, each of which is a mirror pair.

The fundamental rule of ZFS is this: If you lose ANY vdev in a pool, any vdev at all, no matter how big or small, then *YOU LOSE THE POOL* to which that vdev is associated. If you took your mirrored pairs down to individual disks, they would be single-disk vdevs, and if lost ANY SINGLE ONE of them, you'd drop a vdev, which means the ***POOL*** dies.

 

[rdx321]

Alright, so the only way I can get something like this to work, is if I setup a pool for each hard drive, and maybe use a symlink on a central path to link all the drives together?

Anyone have any other ideas how I can get a two machine setup going without mirroring so I don't loose all the data if one drive fails on one particular machine?