Date: Fri, 25 Mar 2022 17:05:06 GMT From: Martin Simmons <martin@lispworks.com> To: Alan Somers <asomers@freebsd.org> Cc: bsdlists@jld3.net, freebsd-fs@freebsd.org Subject: Re: mirror vdevs with different sizes Message-ID: <202203251705.22PH56du029811@higson.cam.lispworks.com> In-Reply-To: <CAOtMX2jdRT1mmDzcPbkN42ruKe6gC5QaHQZRMmHeup=C562wFA@mail.gmail.com> (message from Alan Somers on Fri, 25 Mar 2022 10:09:39 -0600) References: <95932839-F6F8-4DCB-AA7F-46040CFA1DE1@jld3.net> <CAOtMX2jdRT1mmDzcPbkN42ruKe6gC5QaHQZRMmHeup=C562wFA@mail.gmail.com>
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Is "the new disks will have a lower ratio of IOPS/TB" another way of saying
"more of the data will be stored on the new disks, so they will be accessed
more frequently"? Or is this something about larger vdevs in general?
__Martin
>>>>> On Fri, 25 Mar 2022 10:09:39 -0600, Alan Somers said:
>
> 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.
> >
>
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