[lug] software RAID

[D. Stimits]

Jeff Schroeder wrote:
> Hugh wrote:
> 
> 
>>I just
>>read something that said putting them on the same ide interface is
>>worse than bad.  If so, is it only performance related or do terrible
>>things happen (guess who put both drives on ide1).
> 
> 
> There are really two reasons not to do that:
> 
> 1) Performance, as you said.  Since you're writing to both drives in a 
> RAID-1 configuration, you'll be crowding the bandwidth on the IDE 
> channel.  Using two channels will allow you to have greater speed.
> 

Worse than that: IDE does not allow two drives simultaneous access. 
Maybe SATA is better, but I don't know. In terms of SCSI, there is a 
fast burst then the drive disconnects from the bus. SCSI has no problem 
dealing with maybe 7 drives on one cable (except perhaps for average 
throughput if they're all accessed at once). IDE though will force the 
drives to take turns. It won't matter what speed you think it is, the 
drive can't disconnect from the bus till the operation is complete (at 
least for regular IDE, somehow I doubt they did any better with 
SATA...if they had it would be called SCSI).

D. Stimits, stimits AT comcast DOT net