On Thu, 9 Apr 2009, John Hughes wrote:
> > So if u need performance a "Software RAID Solution" would always be a bad
> > choice.
> Why? Do you have any benchmarks that show that software raid is slower than
> hardware raid?
For RAID 1 and 0, software RAID is as fast or faster in my experience.
If you think about it, the software is just coordinating DMA transfers,
no actual processing. It is RAID 5 and similar configurations that benefit
from hardware implementation. My experience has been with the 'md' driver
and AIX LVM, not with Linux LVM mirroring/striping, however.
A big drawback of controller based hardware RAID is the requirement
to have same sized drives (or waste the difference). With software RAID (and
with high end sub-system based hardware RAID), you can mix a variety of drive
sizes. I typically use RAID 1, and I like to expand storage by just
adding a drive in the size du jour (500G today, 1T tomorrow), and doing
a few pvmoves to expand mirrored space. (And you can also move md
mirrors while in operation with judicious use of mdadm -a and mdadm -f,
the tricky part being no changes to a partition table while a partition is
in use).
--
Stuart D. Gathman <stuart@bmsi.com>
Business Management Systems Inc. Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.
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