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Migrating RAID: Degraded RAID5 from RAID1?

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danthehat at gmail

Nov 27, 2009, 2:32 PM

Post #1 of 4 (246 views)
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Migrating RAID: Degraded RAID5 from RAID1?

Hello list,

Currently I have two terabyte hard disks in a RAID1 configuration
using software RAID. What I'd like to do is add a third disk and
arrive at the end with a RAID5 array. The problem is I have limited
disk space and not enough room to back up all of the data on the array
in its current form. What I'd like to know is if it is possible to
use two disks to make a degraded RAID5 array, move the data onto it
from one of the mirror disks, and then add the mirrored disk into the
new array?

Thanks,
D

ubergitler at yandex

Nov 27, 2009, 11:30 PM

Post #2 of 4 (215 views)
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Re: Migrating RAID: Degraded RAID5 from RAID1? [In reply to]

let suppose
sda and sdb is raid 1 md1
and new sdc
remove sdb from raid
mdadm /dev/md1 -f /dev/sdb
mdadm /dev/md1 -r /dev/sdb
then create degraded raid 5
don't forget md1 is still running
mdadm --create /dev/md2 --level 5 -n 3 /dev/sdb /dev/sdc missing
then copy all data from md1 to md2
fix /etc/fstab and /boot/grub/grub.conf
destroy md1
and add sda to md2

2009/11/28 Dan Cowsill <danthehat [at] gmail>

> Hello list,
>
> Currently I have two terabyte hard disks in a RAID1 configuration
> using software RAID. What I'd like to do is add a third disk and
> arrive at the end with a RAID5 array. The problem is I have limited
> disk space and not enough room to back up all of the data on the array
> in its current form. What I'd like to know is if it is possible to
> use two disks to make a degraded RAID5 array, move the data onto it
> from one of the mirror disks, and then add the mirrored disk into the
> new array?
>
> Thanks,
> D
>
>

--
Ларин Андрей

тел 89093090949

danthehat at gmail

Nov 29, 2009, 6:28 AM

Post #3 of 4 (210 views)
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Re: Migrating RAID: Degraded RAID5 from RAID1? [In reply to]

On Sat, Nov 28, 2009 at 2:30 AM, andrey larin <ubergitler [at] yandex> wrote:
> let suppose
> sda and sdb is raid 1 md1
> and new sdc
> remove sdb from raid
> mdadm /dev/md1 -f /dev/sdb
> mdadm /dev/md1 -r /dev/sdb
> then create degraded raid 5
> don't forget md1 is still running
> mdadm --create /dev/md2 --level 5 -n 3 /dev/sdb /dev/sdc missing
> then copy all data from md1 �to md2
> fix /etc/fstab and /boot/grub/grub.conf
> destroy md1
> and add sda to md2

Excellent. All I need to know is that there is indeed a mechanism for
doing this and that I am not crazy. Man pages should fill in the
rest.

Thanks for your help, Andrey

volkerarmin at googlemail

Nov 29, 2009, 7:32 AM

Post #4 of 4 (214 views)
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Re: Migrating RAID: Degraded RAID5 from RAID1? [In reply to]

On Freitag 27 November 2009, Dan Cowsill wrote:
> Hello list,
>
> Currently I have two terabyte hard disks in a RAID1 configuration
> using software RAID. What I'd like to do is add a third disk and
> arrive at the end with a RAID5 array. The problem is I have limited
> disk space and not enough room to back up all of the data on the array
> in its current form. What I'd like to know is if it is possible to
> use two disks to make a degraded RAID5 array, move the data onto it
> from one of the mirror disks, and then add the mirrored disk into the
> new array?
>
> Thanks,
> D
>

easy, have a look at 'grow'. Oh and use google. There are a lot of examples
how to go from raid1 to raid5. It is easy. No disk pulling is needed.

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