[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Survey .. how many domains do you host? (Now RAID)

On Sat, 3 Nov 2001 01:19, Jason Lim wrote:
> Hum... if the Highpoint chipsets are merely IDE controllers... whats the
> advantage to using them over the regular plain vanilla generic IDE
> controller cards?
> Don't they offload ANY work from the processor at ALL? They have to have
> SOME sort of benefit... otherwise, why market them as RAID controllers?

For RAID-0 the only work is to do a translation:
drive = blocknum % 2;
drive_blocknum = blocknum / 2;

For RAID-1 the only work is to decide which drive has a shorter queue for 
reading and to write the same data to both drives for writing, and of course 
the rebuild on reboot.

It's not so much work.  The benefit of hardware RAID (including BIOS software 
RAID) for RAID-0 and RAID-1 is to enable booting from the RAID without any 

RAID-5 is another issue though.  But then you have to consider that Linux 
software RAID kills the performance of most hardware RAID controllers.  Run 
an Athlon 800 with two IDE drives in RAID-1 and expect 2-4 times the 
performance for bulk IO that an entry level Mylex RAID controller with Ultra2 
SCSI 10K rpm drives.  I expect that a top-end Mylex controller will perform 
well (but who can afford one of them?).

http://www.coker.com.au/bonnie++/     Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/       Postal SMTP/POP benchmark
http://www.coker.com.au/projects.html Projects I am working on
http://www.coker.com.au/~russell/     My home page

Reply to: