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Re: Onboard raid controllers a problem?

On Fri, Sep 23, 2005 at 07:43:19AM -0400, Steve Dondley wrote:
> Thanks for all the useful advice.  One follow-up question: should I
> spring for a genunie hardware controller card?  Or is a Linux software
> RAID "good enough?"

Depends what you like.

If you want to do raid5, some hardware raid cards have nice chips for
doing the xor calculations quickly, while doing raid5 in software uses
quite a bit more cpu.

raid1 is simple to do in software and hardware raid doesn't make it
faster.  It does make it simpler to rebuild the raid after a disk
failure though since on most hardware raid cards it can detect hot
swapped disks and automatically rebuild the raid, while with software
raid you have to tell it to start the rebuild, and there is currently no
support for hotswap ide or sata (although sata hotswap is being worked
on) as far as I know.

If you don't mind shutting down the system to remove a failed disk and
adding a new disk, then booting and rebuilding the raid, then software
raid works fine.  Certainly costs less too.

Hardware raid is simpler (usually) to set since you just tell it what to
setup and you see plain disks in linux that you just use as if they were
normal disks without worrying about the raid details and where the boot
loader should go.

You can boot from hardware raid5, but not from software raid5.  You can
boot from software raid1 though.

Len Sorensen

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