On Tuesday, 14 January 2003 at 9:16:22 -0500, Bill Moran wrote: > Ion-Mihai Tetcu wrote: >> Hi, >> >> I have to setup a database (MySQL) server this days. >> The machine will be a AthlonXP 2000+, 1G RAM, 2x Cheetah X15 36LP series >> drive of 18GB. >> And I could spare a 20G ATA100 IDE drive. >> >> I have no experience with vinum, so i want to ask you if it is a good >> ideea to add the IDE drive. I was thinking to use it as a backup drive >> in case the SCSI controller fail. I'm courios about what impact will >> have on the performance of the system and as the server will have to >> enter in production in a few days I do not have the time to play with. > > I'm not going to take the time to research the specs on each of > those drives. However, if the ATA drive is slower than the others, > and you configure the three in a striping configuration, the total > speed of the array will be limited by the slowest drive.
For some definition of total speed. A better way to look at it is at the total bandwidth. It will obviously be lower if one of the disks is slower. > (The same would be true of a mirroring config, but you don't > generally do that with 3 drives) No, with mirroring the slowest drive would slow down the others on writes, because they always go to both disks. That's not the case with striping. > If you config them as concatenated, or with different partitions, > the speed will depend on which drive is being accessed. Yes, that's the case with striping too. You shouldn't make more than one disk access per I/O request, otherwise latency kills you. > So the answer is: whether or not it's a good idea depends on how you > configure it. If you configure the ATA as temp space, and the > Cheetahs as database storage space, you'll probably see better > performance than if both were on one drive, since writing to both > ATA & SCSI simultaneously should go faster than trying to write temp > and data to one drive at once. However, even this depends on your > motherboard and controller, so your actual performance is going to > depend. Unless someone else has used your exact config and done > benchmarks, there's no way to be 100% sure. Note that there's no a priori reason to believe that the ATA drive is going to be slower than the SCSI drives. My own take on this: it should work, and performance shouldn't be markedly different from a 3 SCSI disk config. How you actually use it depends very much on your intended use, though. Greg -- When replying to this message, please copy the original recipients. If you don't, I may ignore the reply or reply to the original recipients. For more information, see http://www.lemis.com/questions.html See complete headers for address and phone numbers To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-questions" in the body of the message