Mike Williams wrote:
Yesterday an IBM ServeRAID decided to mark it's 3 SCSI disks as defunct when
they are all in fact perfectly fine, giving me a 4am finish this morning
after the major hassle of rebuilding, so I'm now heavily biased against
hardware RAID, when I know software RAID is fully capable.
Plus, mdadm can give you all the information you could ever need, and bugs get
squashed quickly. http://bugzilla.kernel.org/show_bug.cgi?id=5181
I think the general consensus is that now CPUs are so cheap, and so powerful,
that they can quite easily offset the extra horsepower needed, unless your
workload is heavily CPU bound.
None of the workloads on any of my servers are heavily CPU bound, so apart
from this one server that came with the card (though an acquision of another
company), all my RAID needs (on some 16 servers) are done in software.
Both software and hardware RAIDs can and will flake at some point so
it's a toss up there. I find hardware a bit easier to work with as I
never need to mess with grub and whatnot to get things to boot correctly.
CPU is just part of the equation in RAID. Assuming I/O is your biggest
problem having a nice 256MB cache on the raid card can change expensive
short writes into nice long writes can really help an underperforming
server.
I'd say if you want raid for better fault tolerance stay with software
raid. If you also need performance spend the money and get a decent RAID
card. Do not get the lame ass winmodem raid cards. You'll have driver
issues and they basically emulate a software raid badly.
kashani
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