Re: Software RAID question

From: Dances With Crows (danSPANceswitTRAPhcrows_at_usa.net)
Date: 08/11/04 

Date: 11 Aug 2004 20:37:51 GMT

On 11 Aug 2004 19:56:44 GMT, Davide Bianchi staggered into the Black Sun
and said:
> On 2004-08-11, Clayton <ctav01@NOSPAMcomcast.net> wrote:
>> from what I've read, software RAID is better than hardware
> Where did you get this impression? Hardware is obviously better, but
> it's more expensive than software.

This depends on the RAID controller and your definition of "better".
The advantage of a hardware RAID is that the controller itself handles
parity checking without bogging down the CPU. The disadvantage of
hardware RAID is that the controller's parity checking can be slower
than having a fast CPU do the checking. Software RAID-1 with a 1GHz
processor is usually faster than hardware RAID-1 with a cheap controller
card. Can't remember the stats for RAID-5 but RAID-5 is more
CPU-intensive than RAID-1.

>> eventually swap out the 60 for a 120 (or larger), will the array
>> resize itself?
> Of course not. You have to resize it. But if you want to do things
> right get disks [that are] all the same size.

In most hardware RAID-5 setups, if you have 3 disks of 10, 20, and 30G,
you can only create an array of ((3-1)*10)G in size. If you use
software RAID, you can partition the non-Redundant portions of the 20
and 30G disks and use them as normal. HTH, 

-- 
Matt G|There is no Darkness in Eternity/But only Light too dim for us to see
Brainbench MVP for Linux Admin /    mail: TRAP + SPAN don't belong
http://www.brainbench.com     /                Hire me! 
-----------------------------/ http://crow202.dyndns.org/~mhgraham/resume

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