On Jan 19, 2006, at 2:23 PM, kashani wrote:
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.
if you do go with software raid...make DARN sure you get grub
installed on both drives, or you're wasting your time. (can you tell
i've been down that road)? I personally prefer hardware raid,
because if you go software raid, I don't believe your /boot partition
can exist on the raid. so each drive would have to have a /boot
partition....or has that need been alleviated?
kashani
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