Data Storage - Need RAID card with online cap expansion

Author

Need RAID card with online cap expansion

lootman@beer.com

2005-02-02, 5:45 pm

I'm looking to build a media server to hold all of my DVDs. I need a
RAID card with Online Capacity Expansion. I need to be able to do two
things related to this:

1) I would like to start with 4 250GB drives in a RAID5. Eventually, I
would like to add more 250GB drives to the array without disturbing the
existing data. So the card needs to recreate the parity drive on the
fly if I expand to 5 - 8 drives.

2) Down the road, I would like to replace the 250GB drives with larger
drives The card needs to handle this by repairing the array as I
remove one 250GB drive and replace with a bigger drive one at a time.
Once all of the new drives are in place, the new capacity needs to be
available to me.

3) What's the best OS to run on this so that a Win MCE2005 system can
access all of the data? XP seems to have the best driver and utility
support with the cards in the $500 range, but I would have to use
Partition Magic if the array changed size wouldn't I? This makes me
think that Fedora w/ LVM might be a better choice.
Thanks for any advice.
Chris

Bill Todd

2005-02-02, 8:45 pm

lootman@beer.com wrote:
> I'm looking to build a media server to hold all of my DVDs. I need a
> RAID card with Online Capacity Expansion. I need to be able to do two
> things related to this:
>
> 1) I would like to start with 4 250GB drives in a RAID5. Eventually, I
> would like to add more 250GB drives to the array without disturbing the
> existing data. So the card needs to recreate the parity drive on the
> fly if I expand to 5 - 8 drives.
>
> 2) Down the road, I would like to replace the 250GB drives with larger
> drives The card needs to handle this by repairing the array as I
> remove one 250GB drive and replace with a bigger drive one at a time.
> Once all of the new drives are in place, the new capacity needs to be
> available to me.
>
> 3) What's the best OS to run on this so that a Win MCE2005 system can
> access all of the data? XP seems to have the best driver and utility
> support with the cards in the $500 range, but I would have to use
> Partition Magic if the array changed size wouldn't I? This makes me
> think that Fedora w/ LVM might be a better choice.
> Thanks for any advice.

Well, if you really mean that...

Lose the RAID card, lose the RAID itself, lose the issue of dynamically
expanding the file system on the RAID. This is a read-only application
(with occasional additions of new DVDs and possibly infrequent deletions
of some no longer desired): all you need to do is make two copies (one
to each member of a manually-defined disk pair) whenever you add a DVD
and delete both copies when you remove one.

What you save on the (large, by your account) RAID card will pay for the
additional disks required to mirror the data manually. If you're really
bent on a minimum-cost system, though, you can always use a software
parity RAID implementation (which would also give you a large,
convenient single file system to work with rather than the multiple
disjoint systems which manual mirroring on individual disks would create
- though then you'd again face the issue of how to expand using more
and/or larger disks, which is not a problem with the individual
manually-mirrored disks: you just add more in the first case, or in the
second just clone the old disks to the new ones with a partition manager
and then expand the file systems on them to fill the space there). With
whatever approach (RAID or manual mirroring) you use, performance in
degraded mode isn't an issue: if you lose a disk, just replace it and
rebuild.

- bill

David A.Lethe

2005-02-03, 2:45 am

On 2 Feb 2005 12:39:33 -0800, lootman@beer.com wrote:

>I'm looking to build a media server to hold all of my DVDs. I need a
>RAID card with Online Capacity Expansion. I need to be able to do two
>things related to this:
>
>1) I would like to start with 4 250GB drives in a RAID5. Eventually, I
>would like to add more 250GB drives to the array without disturbing the
>existing data. So the card needs to recreate the parity drive on the
>fly if I expand to 5 - 8 drives.
>
>2) Down the road, I would like to replace the 250GB drives with larger
>drives The card needs to handle this by repairing the array as I
>remove one 250GB drive and replace with a bigger drive one at a time.
>Once all of the new drives are in place, the new capacity needs to be
>available to me.
>
>3) What's the best OS to run on this so that a Win MCE2005 system can
>access all of the data? XP seems to have the best driver and utility
>support with the cards in the $500 range, but I would have to use
>Partition Magic if the array changed size wouldn't I? This makes me
>think that Fedora w/ LVM might be a better choice.
>Thanks for any advice.
>Chris
I'd go with the 3ware 9500 family of SATA RAID cards. Lots if
intelligence, and they have 4, 8, and 12 drive versions, and support
expansion.

Unless you have a power or space problem, I would not recommend
replacing drives with higher density disks. Just add more disks or
RAID controllers, and go with external cabinetry.

"Best" is relative, but if you are committed to using MCE2005, then
I'd be inclinded to go down the MSFT O/S path so you don't give them
reason to point fingers when you have problems like dropped frames.