Re: [K12OSN] SCSI Disk subsystems was: Building a new lab server...recommendations?

[Eric Harrison <eharrison mail mesd k12 or us>]

On 1 Apr 2003, Immanuel Derks wrote:

>Op di 01-04-2003, om 06:53 schreef Terrell Prude', Jr.:
>Sounds very reasonable to me and exactly my findings concerning single scsi channel raid setups: I have seen respectable performance in good relation to bus width and amount of disks
>attached.
>That's why I'm so confused to have only 47MB/s on a single channel scsi-320 Raid0 setup with a hardware SeveRAID-5i controller (128MB cache).
>Disks also scsi320 15000rpm 'course.
>It should scream at least double that speed otherwise it is simply not worth the investment and besides the point having hardware raid controllers.
>It would then be more interesting financially,performance wise and for redundancies sake to do software raid on two channels.
>I just hope my controller is broken to account for the abominable bad performance....(do we keep on trusting IBM hardware?)
>
>Alla, still hope some scsi320 server out there with a hardware controller on a single channel raid setup can push some hdparm's to the list :)
>
>Kind regards, Immanuel

Here's a couple "hdparm"'s for a few of the scsi-based systems I happened
to be logged into at the moment. Keep in mind that these benchmarks are
fairly meaningless, as has been pointed out in previous postings....


three ultra 160 drives w/software raid 5:
	# hdparm -t /dev/md0
	/dev/md0:
	 Timing buffered disk reads:  64 MB in  0.85 seconds = 75.68 MB/sec


two ultra 160 drives w/software raid 1:
	# hdparm -t /dev/md0
	/dev/md0:
	 Timing buffered disk reads:  64 MB in  1.22 seconds = 52.59 MB/sec


single ultra 160:
	# hdparm -t /dev/sda
	/dev/sda:
	 Timing buffered disk reads:  64 MB in  1.72 seconds = 37.24 MB/sec


old, single ultra wide scsi (40/mbps):
	# hdparm -t /dev/sda
	/dev/sda:
	 Timing buffered disk reads:  64 MB in  3.61 seconds = 17.73 MB/sec


ancient, single ultra scsi (20/mbps):
	# hdparm -t /dev/sda
	/dev/sda:
	 Timing buffered disk reads:  64 MB in  9.67 seconds = 6.62 MB/sec