PERC4/DC : Convert single-disk RAID0 to dual-disk RAID1 and preserve data?

Kuba Ober kuba at mareimbrium.org
Wed Feb 28 08:55:36 CST 2007


On Wednesday 28 February 2007, Kuba Ober wrote:
> On Wednesday 28 February 2007, vincent at cojot.name wrote:
> > Hello everyone,
> >
> > I have a system using a single-disk SCSI config in a single logical drive
> > on a PERC 4e/DC. I have obtained an identical SCSI disk and I'd like to
> > convert the system to RAID-1. I.E: The original single disk would become
> > part (and retain its OS/data on it!)  of a RAID-1 logical drive.
> >
> > Typically, this would most likely involve creating a RAID-1 with a single
> > disk survivor, add another disk later and resync the second disk drive.
> > However, the PERC4 won't let me create a single-disk RAID-1, only RAID-0
> > is allowed.
>
> Did you try doing it from the controller's BIOS? I find that it's way more
> tolerant of one's intentions. The OMSA is web-based unitlity is quite
> limiting IMHO. The command line omconfig may let you do what you want to
> do, although I haven't tried.

Well, omconfig doesn't let you create a degraded RAID-1. :(

Unfortunately, it looks like Dell wants you to have some cold spares on hand, 
and use those to move stuff around. It becomes a pity when all drive bays are 
populated and there's nowhere to add the temporary drive.

I almost can't believe that 5 years ago Linux software RAID was more potent 
than PERC's are today. It'd be a nice hack to get a tiny Linux setup running 
on PERC's CPU :)

The only thing keeping me from using Linux's software RAID on my 2650 and 2850 
is that the data ultimately flows though the CPU's cache, and that's bad for 
computational performance (think Asterisk and codecs) when lots of disk data 
are moved around.

Kuba



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