Is RAID1 to RAID5 conversion possible?

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Is RAID1 to RAID5 conversion possible?

Bob Williams
Hi,

I have two 1TB disks configured as a Linux software RAID1 array and
mounted on /home. There is 385GB free space. I am about to get a new
machine, which will come with a 1TB disk. After I've removed Windows
Vista from this disk I would like to add it to the array. If I stay with
RAID1, I'll gain some redundancy, but no extra storage space. That's
cool, as I've still got that 385GB free space. I have another, smaller
disk to hold the OS partitions.

However, at some stage it might be better to configure the three disks as
RAID5. Is it possible to convert a RAID1 array into a RAID5 array without
loss of data. If not, it might be better to do the conversion now, while
I can still find space to backup /home.

I'd welcome some advice :)

Bob
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Re: Is RAID1 to RAID5 conversion possible?

Bugzilla from jc@phocean.net
Hi,

I think you did not search much. A link I quickly found with google :
http://mindache.net/wp/2008/02/18/raid1-to-raid5-with-lvm-resizing

This is well explained : it consists in creating a degraded RAID 5 with
only 2 disks, transfer your data and then complete the RAID 5.

JC


Le vendredi 05 décembre 2008 à 20:22 +0000, Bob Williams a écrit :

> Hi,
>
> I have two 1TB disks configured as a Linux software RAID1 array and
> mounted on /home. There is 385GB free space. I am about to get a new
> machine, which will come with a 1TB disk. After I've removed Windows
> Vista from this disk I would like to add it to the array. If I stay with
> RAID1, I'll gain some redundancy, but no extra storage space. That's
> cool, as I've still got that 385GB free space. I have another, smaller
> disk to hold the OS partitions.
>
> However, at some stage it might be better to configure the three disks as
> RAID5. Is it possible to convert a RAID1 array into a RAID5 array without
> loss of data. If not, it might be better to do the conversion now, while
> I can still find space to backup /home.
>
> I'd welcome some advice :)
>
> Bob
> --
> Registered Linux User #463880 FSFE Member #1300
> GPG-FP: A6C1 457C 6DBA B13E 5524 F703 D12A FB79 926B 994E
> openSUSE 11.0, Kernel 2.6.25.18-0.2-default, KDE 3.5.10
> Intel Celeron 2.53GHz, 2GB DDR RAM, nVidia GeForce 7600GS

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Re: Is RAID1 to RAID5 conversion possible?

gregfreemyer
>
>
> Le vendredi 05 décembre 2008 à 20:22 +0000, Bob Williams a écrit :
>> Hi,
>>
>> I have two 1TB disks configured as a Linux software RAID1 array and
>> mounted on /home. There is 385GB free space. I am about to get a new
>> machine, which will come with a 1TB disk. After I've removed Windows
>> Vista from this disk I would like to add it to the array. If I stay with
>> RAID1, I'll gain some redundancy, but no extra storage space. That's
>> cool, as I've still got that 385GB free space. I have another, smaller
>> disk to hold the OS partitions.
>>
>> However, at some stage it might be better to configure the three disks as
>> RAID5. Is it possible to convert a RAID1 array into a RAID5 array without
>> loss of data. If not, it might be better to do the conversion now, while
>> I can still find space to backup /home.
>>
>> I'd welcome some advice :)
>>
>> Bob

On Fri, Dec 5, 2008 at 4:44 PM, Jean-Christophe Baptiste <[hidden email]> wrote:
> Hi,
>
> I think you did not search much. A link I quickly found with google :
> http://mindache.net/wp/2008/02/18/raid1-to-raid5-with-lvm-resizing
>
> This is well explained : it consists in creating a degraded RAID 5 with
> only 2 disks, transfer your data and then complete the RAID 5.
>
> JC

That requires 4 disks, not the 3 asked about.

If you have your data backed up, or otherwise recreate-able (and I hope you do).

You can:

degrade the 2-disk array to a single disk.

Use the disk you just freed up and the new disk to build a degraded
3-disk raid-5.

Migrate your data from the Raid-1 to the raid-5.

Then destroy the raid-1 and add the last remaining disk into the raid-5.

Personally, I'd buy a 4th drive and follow the procedure in the link.

Greg
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Re: Is RAID1 to RAID5 conversion possible?

Bugzilla from jc@phocean.net
I guess you meant : 
> Use the disk you just freed up and the new disk to build a degraded
> 2-disk raid-5.

I thought it was easy to guess from the link. I am sure it will make it.

Le vendredi 05 décembre 2008 à 17:24 -0500, Greg Freemyer a écrit :

> >
> >
> > Le vendredi 05 décembre 2008 à 20:22 +0000, Bob Williams a écrit :
> >> Hi,
> >>
> >> I have two 1TB disks configured as a Linux software RAID1 array and
> >> mounted on /home. There is 385GB free space. I am about to get a new
> >> machine, which will come with a 1TB disk. After I've removed Windows
> >> Vista from this disk I would like to add it to the array. If I stay with
> >> RAID1, I'll gain some redundancy, but no extra storage space. That's
> >> cool, as I've still got that 385GB free space. I have another, smaller
> >> disk to hold the OS partitions.
> >>
> >> However, at some stage it might be better to configure the three disks as
> >> RAID5. Is it possible to convert a RAID1 array into a RAID5 array without
> >> loss of data. If not, it might be better to do the conversion now, while
> >> I can still find space to backup /home.
> >>
> >> I'd welcome some advice :)
> >>
> >> Bob
>
> On Fri, Dec 5, 2008 at 4:44 PM, Jean-Christophe Baptiste <[hidden email]> wrote:
> > Hi,
> >
> > I think you did not search much. A link I quickly found with google :
> > http://mindache.net/wp/2008/02/18/raid1-to-raid5-with-lvm-resizing
> >
> > This is well explained : it consists in creating a degraded RAID 5 with
> > only 2 disks, transfer your data and then complete the RAID 5.
> >
> > JC
>
> That requires 4 disks, not the 3 asked about.
>
> If you have your data backed up, or otherwise recreate-able (and I hope you do).
>
> You can:
>
> degrade the 2-disk array to a single disk.
>
> Use the disk you just freed up and the new disk to build a degraded
> 3-disk raid-5.
>
> Migrate your data from the Raid-1 to the raid-5.
>
> Then destroy the raid-1 and add the last remaining disk into the raid-5.
>
> Personally, I'd buy a 4th drive and follow the procedure in the link.
>
> Greg
> --
> Greg Freemyer
> Litigation Triage Solutions Specialist
> http://www.linkedin.com/in/gregfreemyer
> First 99 Days Litigation White Paper -
> http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf
>
> The Norcross Group
> The Intersection of Evidence & Technology
> http://www.norcrossgroup.com

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Re: Is RAID1 to RAID5 conversion possible?

Bob Williams
In reply to this post by Bugzilla from jc@phocean.net
On Friday 05 December 2008 21:44:59 Jean-Christophe Baptiste wrote:
> Hi,
>
> I think you did not search much. A link I quickly found with google :
> http://mindache.net/wp/2008/02/18/raid1-to-raid5-with-lvm-resizing
>
> This is well explained : it consists in creating a degraded RAID 5 with
> only 2 disks, transfer your data and then complete the RAID 5.
>
> JC

Many thanks. You're right, I should google more.

Having read Scott Wallace's link, it looks as if I could transfer all my
disks (2 x 1TB as the RAID1 array and 250GB which holds /, /usr, /var and
swap) into my new machine, boot to level 3, stop /dev/md0, create the new
RAID5 array, then add the third new disk. Scott Wallace booted using a
rescue disk for the first stage, but I assume that is because his OS was
on the RAIDed array.

Of course, I will backup all my data, but it looks as though the data
survives the conversion process, which is good news.

Bob
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Re: Is RAID1 to RAID5 conversion possible?

Bob Williams
In reply to this post by gregfreemyer
On Friday 05 December 2008 22:24:26 Greg Freemyer wrote:

> That requires 4 disks, not the 3 asked about.
>
> If you have your data backed up, or otherwise recreate-able (and I hope
> you do).
>
> You can:
>
> degrade the 2-disk array to a single disk.
>
> Use the disk you just freed up and the new disk to build a degraded
> 3-disk raid-5.
>
> Migrate your data from the Raid-1 to the raid-5.
>
> Then destroy the raid-1 and add the last remaining disk into the
> raid-5.
>
> Personally, I'd buy a 4th drive and follow the procedure in the link.
>
> Greg

The new mainboard only has connectors for four SATA drives. I currently
boot from a single (non-RAIDed) 250GB drive, which holds /, /usr, /var
and swap, while /dev/md0 (the two 1TB drives) is mounted on /home. If I
buy a fourth 1TB drive I'd also need to get a SATA controller card, plus
I don't know that I need all that space at the moment. As it is I'll have
to think how to partition the 2TBs (or will it be 3?) that I'll get from
a 3 x 1TB RAID5 array.

Many thanks for your advice.

Bob
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Re: Is RAID1 to RAID5 conversion possible?

Carlos E. R.-2
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Hash: SHA1



On Saturday, 2008-12-06 at 09:28 -0000, Bob Williams wrote:

> The new mainboard only has connectors for four SATA drives. I currently
> boot from a single (non-RAIDed) 250GB drive, which holds /, /usr, /var
> and swap, while /dev/md0 (the two 1TB drives) is mounted on /home. If I
> buy a fourth 1TB drive I'd also need to get a SATA controller card, plus

Not really. You can put it externally via usb. For example, you can backup
your data to the external disk, then delete your existing raid and create
the new one. You could even create a raid on two external disks via usb!
Of course, slow. Better do two backups. Or you coud add a card for eSATA.

- --
Cheers,
        Carlos E. R.

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Re: Is RAID1 to RAID5 conversion possible?

Bob Williams
On Saturday 06 December 2008 13:26:44 Carlos E. R. wrote:

> On Saturday, 2008-12-06 at 09:28 -0000, Bob Williams wrote:
> > The new mainboard only has connectors for four SATA drives. I
> > currently boot from a single (non-RAIDed) 250GB drive, which holds /,
> > /usr, /var and swap, while /dev/md0 (the two 1TB drives) is mounted
> > on /home. If I buy a fourth 1TB drive I'd also need to get a SATA
> > controller card, plus
>
> Not really. You can put it externally via usb. For example, you can
> backup your data to the external disk, then delete your existing raid
> and create the new one. You could even create a raid on two external
> disks via usb! Of course, slow. Better do two backups. Or you coud add
> a card for eSATA.
>
> --
> Cheers,
>         Carlos E. R.

I'm beginning to realise just how many choices/decisions there are :)

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