[Beowulf] hardware RAID versus mdadm versus LVM-striping

Rahul Nabar rpnabar at gmail.com
Sun Jan 17 23:01:50 EST 2010


On Sun, Jan 17, 2010 at 9:58 PM, Joe Landman
<landman at scalableinformatics.com> wrote:

> Its a software RAID implementation pretending to be a hardware RAID
> implementation.  They are rarely if ever as good as MD.  Many of them in
> Linux will invoke dm (the "other" RAID engine) as dm has "support" for
> fake-raid.  Note that we have lost data (multiple times) with dm+fake-raid
> in testing, so we don't recommend its use in important machines (ones which
> you can't afford to lose).  This could be due to bad drivers for the chips
> in question, but we aren't taking chances.

Ah! Thanks for the tip. I thought the line between hardware and
software was clear cut. Any way to oust such an impostor RAID? What
signs would it show?  If the hardware in fact does use system software
and CPU  I can find out by looking for a specific daemon etc? Or maybe
CPU loads?

-- 
Rahul

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