On Tue, 6 Nov 2001 07:26, Dave Watkins wrote: > Not to start a holy war, but there are real reasons to use SCSI. > > The big ones are > > Much larger MTBF,
Mean Time Between Failures is not such a big deal when you run RAID. As long as you don't have two drives fail at the same time. Cheaper IDE disks make RAID-10 more viable, RAID-10 allows two disks to fail at the same time as long as they aren't a matched pair. So a RAID-10 of IDE disks should give you more safety than a RAID-5 of SCSI. > faster access times due to higher spindle speeds, better When doing some tests on a Mylex DAC 960 controller and a Dual P3-800 machine I found speed severely limited by the DAC. The performance on bulk IO for the 10K rpm Ultra2 SCSI drives was much less than that of ATA-66 drives. > bus management (eg 2 drives can perform tasks at once unlike IDE), Hot See http://www.coker.com.au/~russell/hardware/46g.png for a graph of performance of an ATA disk on it's own, two ATA disks running on separate busses, and two disks on the same bus. From that graph I conclude that most of the performance hit of running two such drives comes from the motherboard bus performance not from an IDE cable. That graph was done with an old kernel (about 2.4.1), I'll have to re-do it with the latest results from the latest kernel. Anyway motherboards with 4 IDE buses on the motherboard are common now, most servers don't have more than 4 drives. > Swapable (This is HUGE) and more cache on the drive. NO! SCSI hard drives are no more swappable than ATA drives! If you unplug an active SCSI bus you run the same risks of hardware damage as you do for ATA! Hardware support for hot-swap is more commonly available for SCSI drives than for ATA, but it is very pricey. -- http://www.coker.com.au/bonnie++/ Bonnie++ hard drive benchmark http://www.coker.com.au/postal/ Postal SMTP/POP benchmark http://www.coker.com.au/projects.html Projects I am working on http://www.coker.com.au/~russell/ My home page