On Tue, Nov 16, 1999 at 03:09:38PM -0500, Otis Gospodnetic wrote:
> Hi,
>
> I have 2 questions here...
>
> 1.
> I'm getting some SCSI disks that I may decide/need to put them in a RAID
> later on.
> I am wondering whether I will be able to preserve all the data on the SCSI
> disks when I convert them to RAID, or will conversion to RAID mean that I'll
> have to lose data on those disks and put it back on the RAID after the
> conversion?
I'm developing a raidreconf utility to allow this. Currently it can ``convert''
a single data disk and a number of empty disks into a RAID-0 while preserving
data.
HOWEVER(!) This has not been tested on large disks (!) I guess it works, and
it's tested on 60-90 MB disks (loopback devices).
When I get a little more spare time I'll add RAID-5 capability.
> 2.
> If I get 2 disks and put them into RAID-0 (striping) what happens when I
> decide to add another (3rd) disk to the setup?
> Does the data automatically migrate from disks 1 and 2 onto 3 so that it is
> evenly spread accross all 3 disks, or would I have to do that manually
> somehow, or is this a bad thing to do and I should just buy all disks that I
> think I will need right away?
> Any advice?
The raidreconf utility can do this with RAID-0 arrays. I've tested it on
a 50+GB RAID, and succesfully expanded it to 100+GB. After expanding the
RAID, I used ext2resize to resize the filesystem. Everything went just
fine.
raidreconf is slow as molasses, but it works - at least for me. Until it has
seen some more testing, I'm reluctant to say that it really works. It does
perform quite a few paranoia checks before actually moving the data, so it
_should_ catch most internal errors, if there are any.
The current algorithm is very clean, eg. it moves data in a way that is simple
and therefore likely to be correct. Therefore it is also very slow. The
expansion of the large array mentioned above took almost 24 hours (!). I'll
optimize this when I get some spare time.
You can get the raidreconf utility as a patch to the raidtools package from
http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
--
................................................................
: [EMAIL PROTECTED] : And I see the elder races, :
:.........................: putrid forms of man :
: Jakob Østergaard : See him rise and claim the earth, :
: OZ9ABN : his downfall is at hand. :
:.........................:............{Konkhra}...............:
