[OpenIndiana-discuss] ZFS 0+1 across disparate drives

[James]

On 01/12/2021 11:55, Michelle wrote:
> I have closing on 12TB of data so even the 10 won't be enough to back
> everything up, but this is as much for the exercise of doing it, as
> achieving anything solid. It won't be under pressure, but I'd rather
> push the envelope and see what I can do.
>
> So how would the command go?
>
> zpool create tank raidz mirror drive1 drive2 mirror drive3 drive4
> drive5
>
> ...which is where I come unstuck with the 2TB drive in the mix.

You are right to be stuck as ZFS can not make a mirror of raid0 in one 
command, zfs is wanting raid0 of mirrors which you can't get to 10TB 
because you don't have pairs.  You can pair the 4&6 and raid0 with 4&4 
and get 8TB of continuous pool.

Partition the 6 into 4 and 2, then you have pairs for raid0 of mirrors. 
Loose the 6TB and you loose 1/2 of 2 mirrors but you are better off than 
loosing 1/2 the entire mirror with mirror of raid0.  10TB using all devices.

Try making 2 raid0 pools 2+4+4 and 4+6, create volumes on those pools 
and use to make a mirror, /dev/zvol/dsk/etc...  Untested and I can't see 
it being better.

Use raidz1 of 4, 4, 4, and 6 = 12TB.  This ignore 2TB of the 6 and you 
get a bonus doorstop by not using the 2TB.  3+1 is not a preferred 
arrangement.