Re: How does one resize/expand a softraid RAID1?

> On 30 Jul 2026, at 15:02, Alexander Hall <[email protected]> wrote:
>>=20
>>=20
>> Not supported with softraid. You can't create a "1-disk RAID1" and =
add
>> the second drive later either. Unless you want to get dirty with =
poking
>> at low level data structures, you'll either need to have both new =
drives
>> and the remaining working old drive connected at the same time and
>> dump/restore, or dump to external media + swap drives + restore, etc.
>=20
>=20
> I don't think the intention is to create a new single-disk RAID1.

I was happy he provided that note, though, because that was the =
=E2=80=9Cother=E2=80=9D
option I=E2=80=99d thought of.

> It sounds more like replacing/rebuilding/"resilver" one underlying =
disk at a time onto a larger RAID partition and then let the sr disk =
grow into them, giving free space at the end of it.

That was my original ask, yes.  Something like that.  The other thought =
I=E2=80=99d
had was maybe trying to make a second one-disk RAID1, then copy the =
data,
then fix the =E2=80=9Cnew=E2=80=9D RAID1 with a matching larger disk.  =
But that was the
less-preferred option.

>=20
>  This might be trickier, but one might be able to force bioctl to =
reinitialize a larger RAID1 on top of the former.
>=20
> Anyway, this probably shouldn't be attempted if you are not ready to =
accept losing your data. Even if so, I would recommend trying it out on =
a smaller scale with some spare drives first.

Yeah, I sent a more recent note asking how plausable these changes would =
be.
But are you saying that I might be able to use bioctl without any =
changes
to kernel or application to =E2=80=9Cforce=E2=80=9D the size to be =
right?  Hmm.  Yeah, that
definitely sounds dangerous to the enclosed file system.  But I think if =
that
is even possible, it makes it clear that it shouldn=E2=80=99t be hard to =
modify the
underlying system to be able to figure that out itself then bioctl could=20=

just have a =E2=80=9Cexpand=E2=80=9D to tell the soft device to grow.  I =
suppose that is
most easily done after both drives are replaced with larger ones, but if =
I
performed the =E2=80=9Ctrick=E2=80=9D of one then the other, which on a =
ZFS mirror allows
it to do this same thing if you=E2=80=99ve turned on =E2=80=9Cautoexpand=E2=
=80=9D; then it seems
like the sr would be the original size on two larger disks and we could =
have
a manual operation triggered with bioctl that will cause the =
=E2=80=9Cexpand=E2=80=9D
operation.  I=E2=80=99m okay with there not being an =E2=80=9Cautoexpand=E2=
=80=9D, as long as
there is a way to cause the expansion by just pushing a [effective] =
button.

But either way, it=E2=80=99s not something that can be done right now in =
7.9.
I=E2=80=99ll proceed with copying the data off, building a new array, =
then copying
the data back.  Luckily, it=E2=80=99s a home server and it being in =
single user
for a couple hours isn=E2=80=99t a big deal.

Thanks all.

-Chris