overlapping partition layout

[O Seidel]

Hello,

discs with 8tb size or maybe even beyond will take a long time to resilver.

When one disc fails, I am afraid the remaining mirror copy is going to fail during the re-silver process.

Now I believe I have this incredibly clever idea ... (not.) Mainly, if my idea was so clever, it would be done already.
And it would be recommended already, so there likely is something wrong with it. Here it goes:

1) take 3x 8tb disc
2) partition them into 4tb pieces a and b each for 1a 1b 2a 2b 3a 3b
3) make a stripe of mirrors "zfs create tank mirror 1b 2a mirror 2b 3a mirror 3b 1a"

I would want to do this because it would put half the load on each of the remaining discs if any one should fail.

Could you please explain where my thinking goes wrong.

Yes, I have used 3-way mirrors before, but if I can use 8x6tb in double mirror or 9x8tb in triple mirror, I get 24tb usable.
The first option is much more economical measured by the benefit I perceive.

Many thanks for your time.

Oliver

 

[Ericloewe]

Performance is rather likely to tank. Up until recently, this was very likely to result in a greater chance of data loss due to longer resilvers. Now there is (or will be soon) the option to sequentially copy the data when resilvering, followed by a normal scrub to verify data integrity.
The resilver proper is still going to be slower, as normal disk I/O will be more erratic than it normally would be if the disk was serving a single vdev.

Managing this also does not sound fun.