[lug] Software RAID5 performance

[Jeff Schroeder]

Daniel wrote:

> I think you have to use software that's designed specifically to test
> drive performance to find the actual transfer rate.  I have always
> used hdparm, but that may only work right directly on IDE devices,
> I'm not sure.

Yeah, I thought so too.  I had run it against the RAID5 and it seemed to 
work:

# hdparm -tT /dev/md0

/dev/md0:
 Timing buffer-cache reads:   1080 MB in  2.00 seconds = 539.81 MB/sec
 Timing buffered disk reads:   66 MB in  3.01 seconds =  21.91 MB/sec

Then, against a "raw" IDE drive:

 # hdparm -tT /dev/discs/disc0/disc 

/dev/discs/disc0/disc:
 Timing buffer-cache reads:   916 MB in  2.00 seconds = 457.16 MB/sec
 Timing buffered disk reads:   72 MB in  3.00 seconds =  23.98 MB/sec

That's comparable performance.  I'd say if it's accurate (meaning, 
hdparm works against software-RAID devices) then the kernel RAID driver 
is amazingly good. :)

Jeff