[Beowulf] Software RAID?

Mark Hahn hahn at mcmaster.ca
Wed Nov 21 20:31:19 EST 2007


>> performance of a commodity RAID card such as LSI/3ware/Areca for
>> direct-attached drives?
>
> Yes.  Of course there's a factor of 10 or more in the various cards
> offered by those vendors.  Adaptec is another popular brand.

I've had good luck with recent 3ware, and heard Areca is good.
both LSI and Adaptec have had really disturbingly slow clunkers 
in their past (we're talking about 10 MB/s products being sold,
new, as recently as 1-2 years ago!)

one kinda sad thing is that there aren't a lot of simple multiport 
cards to do large MD systems with.  4pt is pretty doable, but I haven't
seen pcie cards that were reasonable in price ($50).  once you get to 8pt,
vendors seem to want to gunk it up with HW raid features, which blows
the price up to $400+.

I am very interested in any testimonials about current dumb or smart
controllers.

I've seen a couple interesting things recently.  one is 8pt sas cards 
from LSI for semi reasonable prices (8pt for $330).  I don't know how well
the fusion-mpt driver works, and I haven't experienced how well it works
to plug sata disks into sas hba ports.

the other recent development is port-multipiers, which let you merge 
~5 SATA disks onto one port.  bandwidth-wise, this makes sense, since 
the link is 3Gb, but a disk typically sustains about .5 Gb.  I'd love 
to hear of any practical experience with PM support (I know it's new 
and somewhat spotty.)

-mark
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