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[NMLUG] More RAID Questions
On Wed, 2005-02-23 at 20:34 -0700, Kyle Petree wrote:
>1) If performance is the issue - go hardware.
I've been 90% convinced for a few months now that t the oft-mentioned
superiority of hardware raid is (or perhaps has become over time.)
almost a complete myth. As in most cases disk throughput is
significantly better in a software raid 5 setup than in a similar setup
on a hardware controller. Additionally you don't have the single point
of failure. (ie you set up redundant inexpensive disks precisely so that
when one dies you can easily replace it and move on, but if the
controller dies three years after that model is off the market... [on a
side note, I'm told that the controller almost never dies])
>I've never done software
>on high demand systems, but I do know that in software raid, in the
>event of an OS crash takes hours to resync the data and during that
>time
>drive performance is abysmal, bringing most systems to their knee's
>until it is done.
This is something I've not considered before and seems to be a very good
point, it took me more than half an hour to sync up a 755G array that
had _no_ data on it. I've not looked at disk performance while an array
was rebuilding, so it could certainly be true that performance is
seriously compromised in this scenario. Of course it's not everyday (or
hopefully not every year) that you'll need to resync the array, but if
'performance at all times' including the couple hours following a disk
swap or whatnot is a serious concern then this should be looked into.
Am I right in that your asserting a (or some I suppose) hardware
controller[s] do[es] not experience significant performance loss when
rebuilding the array?
Sam
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