Re: mirror vdevs with different sizes

There's nothing wrong with doing that.  The performance won't be
perfectly balanced, because the new disks will have a lower ratio of
IOPS/TB.  But that's fine.  Go ahead.
-Alan

On Fri, Mar 25, 2022 at 9:17 AM John Doherty <bsdlists@jld3.net> wrote:
>
> Hello, I have an existing zpool with 12 mirrors of 8 TB disks. It is
> currently about 60% full and we expect to fill the remaining space
> fairly quickly.
>
> I would like to expand it, preferably using 12 mirrors of 16 TB disks.
> Any reason I shouldn't do this?
>
> Using plain files created with truncate(1) like these:
>
> [root@ibex] # ls -lh /vd/vd*
> -rw-r--r--  1 root  wheel   8.0G Mar 25 08:49 /vd/vd0
> -rw-r--r--  1 root  wheel   8.0G Mar 25 08:49 /vd/vd1
> -rw-r--r--  1 root  wheel    16G Mar 25 08:49 /vd/vd2
> -rw-r--r--  1 root  wheel    16G Mar 25 08:49 /vd/vd3
>
> I can first do this:
>
> [root@ibex] # zpool create ztest mirror /vd/vd{0,1}
> [root@ibex] # zpool list ztest
> NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP
> HEALTH  ALTROOT
> ztest  7.50G   384K  7.50G        -         -     0%     0%  1.00x
> ONLINE  -
>
> And then do this:
>
> [root@ibex] # zpool add ztest mirror /vd/vd{2,3}
> [root@ibex] # zpool list ztest
> NAME    SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP
> HEALTH  ALTROOT
> ztest    23G   528K  23.0G        -         -     0%     0%  1.00x
> ONLINE  -
>
> And FWIW, everything works as expected. But I've never constructed a
> real zpool with vdevs of different sizes and I don't know whether there
> might be any expected problems.
>
> I could just create a new zpool with new disks, but most of the existing
> data and most of the expected new data is in just two file systems and
> for simplicity's sake from the perspective of those users, it would be
> nicer to just make the existing file systems larger than to give them
> access to a new, different one.
>
> Any comments, suggestions, warnings, etc. much appreciated. Thanks.
>