[ATrpms-users] atrpms kernel modules

[Axel Thimm]

On Thu, Aug 17, 2006 at 11:08:07PM +1000, Jean-Yves Avenard wrote:
> On 8/17/06, Axel Thimm <Axel.Thimm at atrpms.net> wrote:
> > For the RAID it needs to be 250GB drives. That's because if I put
> > 2x500GB I would need to create a new RAID volume which requires
> > one driver to be used for RAID. If I add 250GB drives to the
> > existing RAID every drive's capacity gets fully added since the
> > RAID5 extras drive is already consumed.
> 
> I have the exact same RAID card, you can not add drives to the RAID
> without rebuilding the whole unit, which means you will loose the
> content of the RAID array. I'm sure that's not what you want to do

I haven't done this before, but the manual promise this to be possible
(9500-S), although not from the BIOS, but rather the web frontend
(availabe at ATrpms) and the console client.

| About Migration
| 
| Migration allows on-line units to be reconfigured. You can make two
| types of configuration changes:
| 
|     * RAID Level
|     * Unit Capacity Expansion
| 
| RAID level migration and unit capacity expansion tasks can be done
| together or separately.
| 
| Migration tasks follow the same schedule as rebuild and initialization
| tasks.
| 
| Because of the controller and disk resources required during
| migration, when migration is active, it has priority over other
| background tasks. When migration starts, it will take the highest
| priority over rebuild, initialize and verify.
| 
| Once a unit is put into the migration state, it must be allowed to
| complete the process. While migrating, rebuilds or verifies to the
| unit are not permitted.
| 
| Migrate tasks are always done in the background, and can be initiated
| through either 3DM or the CLI. (Foreground migrations through 3BM are
| not supported.)
| 
| A unit be migrated can still be used (I/O still continues), however
| the performance will be affected while the migrating task is
| active. You can control how much affect this has on performance by
| setting the background task rate. For more information, see Setting
| Background Task Rate

> If you add two drives, you can get into the card utility (you press
> Ctrl-A I think at boot time) and you create a new array with the two
> drives as a RAID1. By default the two disks will appear a BOD (bunch
> of disk)
> 
> They will appear as one disk in linux which you can add very easily
> in the LVM (provided your existing RAID5 array is in a LVM
> 
> > E.g. with 2x500GB one gets 500GB netto, with 2x250GB one gets the
> > same, and with 3x250GB one gets 750GB.
> 
> it won't help you to use the exact same drives

Doesn't RAID5 operate best when all drives spin at the same speed when
over the same cylinder?
-- 
Axel.Thimm at ATrpms.net
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