Migrating from raid1 to raid10
Lasse
I reckon there are people here who can help me with my issue..?
I have a 2-disk NAS on which I run Debian. It is currently set up in a
raid1 configuration. I am trying to squeeze some better performance
out of this box and thinking about migrating it to raid10 (f2-layout).
I would like to do this without involving any extra/external disks
(apart from the obligatory backup) or reinstalling the OS.
My theory is that I should be able to put the old raid1 array into
degraded mode by failing one of the disks with mdadm and use the freed
disk to create a new raid10 array with a missing disk. Then, rsync the
data, switch arrays in fstab and reboot. Finally remove the last disk
from the old array and add it to the new array...
Are there any reasons why this shouldn't work, and what have I
forgotten..?
Kind regards,
Lars
Aragorn
identifying as Lasse wrote...
> Are there any reasons why this shouldn't work, [...
Yes. :-)
> ...] and what have I forgotten..?
The fact that RAID 10 requires *four* disks, perhaps? :p
http://en.wikipedia.org/wiki/RAID_10#RAID_10_.28RAID_1.2B0.29
--
*Aragorn*
(registered GNU/Linux user #223157)
David Brown
> On Monday 28 December 2009 15:35 in comp.os.linux.setup, somebody
> identifying as Lasse wrote...
>
>> Hi,
>>
>> I reckon there are people here who can help me with my issue..?
>>
>> I have a 2-disk NAS on which I run Debian. It is currently set up in a
>> raid1 configuration. I am trying to squeeze some better performance
>> out of this box and thinking about migrating it to raid10 (f2-layout).
>> I would like to do this without involving any extra/external disks
>> (apart from the obligatory backup) or reinstalling the OS.
>>
>> My theory is that I should be able to put the old raid1 array into
>> degraded mode by failing one of the disks with mdadm and use the freed
>> disk to create a new raid10 array with a missing disk. Then, rsync the
>> data, switch arrays in fstab and reboot. Finally remove the last disk
>> from the old array and add it to the new array...
>>
This should work fine - but be prepared for it to take a good while, and
of course it is a risky operation. Make sure all your data is backed
up, check that the backups are good and can be restored, and then back
up to a second source just to be sure. And make sure you have all
necessary installation CDs, etc., in case things go wrong.
Don't expect wonders from raid10 on two disks - it will be faster than
raid1 for some types of usage, but not /hugely/ faster.
>> Are there any reasons why this shouldn't work, [...
>
> Yes. :-)
>
>> ...] and what have I forgotten..?
>
> The fact that RAID 10 requires *four* disks, perhaps? :p
>
> http://en.wikipedia.org/wiki/RAID_10#RAID_10_.28RAID_1.2B0.29
>
Linux raid 10 does not require 4 disks - it will work fine with any
number of disks (greater than 1). Linux software raid 10 means having
(at least) two copies of everything on different disks, but arranged in
a "stripy" sort of way so that you get the performance benefits of
striping, with the reliability benefits of mirroring.
<http://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10>