[K12OSN] Linux "Software RAID"

[Almquist Burke]

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On Aug 9, 2008, at 8:19 AM, David Hopkins wrote:

> I"ve enjoyed reading this thread, but have a question: I thought one
> of the reasons to continue using RAID 5 vs RAID 1 was speed.  Tests on
> my systems show that the RAID 5 I/O is at least 3x the speed of RAID
> 1.

	How many disks in the RAID 5? And are they all the same size/speed?  
I'm actually fond of RAID 10 (Striping across multiple mirrors) on  
SATA drives.  The downside is that you still loose half your disk  
space, as you would in any RAID 1 array (although SATA drives are so  
big now I don't worry about that). On the upside, it's easy to do in  
software, and gives you better redundancy than 4 disks in RAID 5.  
IMHO having 4 or 6 7200 SATA disks in RAID 10 should be pretty fast  
and costs less and stores more than 4 SCSI disks in RAID 5.
	RAID 5 is more efficient with disk space, and that's the only reason  
to prefer it to RAID 1 or 10, I don't worry about RAID 5 with SATA  
drives, but SCSI drives of the same size are so much more expensive,  
so if you are using those fast SCSI drives then a RAID 5 makes sense  
to preserve your (relatively) expensive disk space. 
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