On Thu, 2 Oct 2008, Joerg Schilling wrote: > > I am not going to accept blanket numbers... If you claim that a 15k drive > offers more than 2x the IOPS/s of a 7.2k drive you would need to show your > computation. SAS and SATA use the same cable and in case you buy server grade > SATA disks, you also get tagged command queuing.
I sense some confusion here on your part related to basic physics. Even with identical seek times, if the drive spins 2X as fast then it is able to return the data in 1/2 the time already. But the best SAS drives have seek times 2-3X faster than SATA drives. In order to return data, the drive has to seek the head, and then wait for the data to start to arrive, which is entirely dependent on rotation rate. These are reasons why enterprise SAS drives offer far more IOPS than SATA drives. > For 10 TB you need ~ 165 73 GB SAS drives -> ~ 22000 Euro > 2475 Watt stand by > ~ 4 GBytes/s sustained > read if you are lucky > and have a good > controller > Max IOPS -> 34000 (not realistic) I am not sure where you get the idea that 34000 is not realistic. It is perfectly in line with the performance I have measured with my own 12 drive array. As I mentioned yesterday, proper design isolates storage which requires maximum IOPS from storage which requires maximum storage capacity or lowest cost. Therefore, it is entirely pointless to discuss how many 73GB SAS drives are required to achieve 10TB of storage since this thinking almost always represents poor design. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
