Upgrading RAID 1 to larger drives...

[Ian R]

Hi

I have a 2TB RAID 1 (mirror) which is running out of room.

I’d like to upgrade the drives to 3TB.

I was wondering about the best way to do it...

If I replace one of the drives with a 3TB I understand that the mirror will
automatically rebuild to the new drive albeit at 2GB. Once that has
completed I replace the remaining 2TB drive with the second 3TB and allow
that to rebuild. Once the rebuild is complete then use a disk manager to
expand the partition to use the max capacity of the new drives?

Is that correct?

Have I missed something or is there a better way?

Thanks for your time and any info.

Ian

[miso]

I would wait for a confirmation from one of the gurus, but it has been
my experience that mirror raid drives can be cloned with the usual
suspects (Ghost for Linux, etc). You just use one of the drives since
they both have the same data.

Here is a thread with the same claim:
> http://forums.anandtech.com/showthread.php?t=2138668

This isn't to say there is some nuance I don't know about. I haven't
dealt with mirror raid in a few years.

Now regarding your trick, I think you will end up with 2Gbyte partitions
on both 3Gbyte drives. But I also believe you can resize mirror raid
partitions with the usual programs and not have an issue. Note you may
have to "break" the mirror at times. How that is done is a function of
how you do your raid, i.e. a controller card, a fake raid (some onboard
chips plus software), or pure software.

Now my personal suggestion is to just hook all the drives up to the PC
and build a fresh 3G mirror raid, and just copy the files. The new
drives can lay on your desk for that part of the operation, though
mounting them in the case or another case is a better idea. Then once
you transfer the data, install the new drives in the case.

If you booted off the raid drive, that is another story. If so, you may
want to consider getting a small SSD for your boot drive. [You can
always clone your small SSD to a cheap USB drive, especially since the
SSD drive wll be small. Thus no need for raid since it only has the OS,
which you can periodically backup.] I'd say at least 160Gbytes per
operating system. Then you won't have the hassles of your OS being on
the raid. Also, I'd go for 4Gbytes, just to save yourself the effort of
doing this all over again.

[Arno]

Ian R <so...@nospam.com> wrote:
> Hi

> I have a 2TB RAID 1 (mirror) which is running out of room.

> I???d like to upgrade the drives to 3TB.

> I was wondering about the best way to do it...

> If I replace one of the drives with a 3TB I understand that the mirror will
> automatically rebuild to the new drive albeit at 2GB. Once that has
> completed I replace the remaining 2TB drive with the second 3TB and allow
> that to rebuild. Once the rebuild is complete then use a disk manager to
> expand the partition to use the max capacity of the new drives?

> Is that correct?

> Have I missed something or is there a better way?

> Thanks for your time and any info.

> Ian

What is your RAID controller?

Anyways, the procedure is always the same: Employ your backup
machanism, upgrade the disks and restore the backup. If you do
not have a backup, it is even easier: Simply throw all your
data away, as it clearly is worthless. Then create a new
RAID array with the new disks. (No, I am not jokeing...).

Arno

[David Brown]

There are various ways to handle this, depending on the sort of data you
have on the disk (is it just files, or is it a bootable OS? Do you need
to preserve the same partitioning? What filesystem is it?), the sort of
raid you have (hardware raid card, fake raid, OS raid, etc.), and the
sort of experience you have (are you happy messing around with scary
utilities, or do you need hand-holding guis?).

Whatever your choices, back up your data. Then back it up a second time
to be sure.

Then run a "scrub" to make sure that all the data is readable on both disks.

If this were my system, I would have the raid1 as Linux md raid. Then
the best method is to attach a third 2 or 3 TB disk, which could well be
on USB if that's the most convenient, and add it to the raid1 for triple
mirroring. After that is synced, swap one of the original 2 TB drives
for a 3 TB drive and sync. Then swap the second 2 TB drive for a 3 TB
and resync. Then you can remove the external disk from the raid and
physically from the machine. grow the raid to fill the whole 3 TB, and
grow the filesystem to use the new space. The external disk is now an
extra backup, and at no point in the process did you ever lose your
redundancy.

Of course, it is possible that you are using an inferior raid system
that doesn't support three-way raid1, in which case the process is
risky, so your backups are essential.