On Tue, 2002-04-23 at 13:57, Ivo Grosse wrote: > Hi Joe, > > Joe Landman <joe.landman@mscsoftware.com> wrote on Tue, 23 Apr 2002: > > > http://www.dell.com/us/en/esg/topics/segtopic_storage_scsi_main.htm you > > see the 160 MB/s throughput. This corresponds to 1280 Mb/s. > > You mean even if that disk array contained only 1 disk, it would give a > w/r flux of 160 MB/s? No. The disk itself (depending upon make, model, etc) can talk anywhere from 10->50 MB/s. The bus it is sitting on can deal with a maximum of 160 MB/s. So you can (theoretically) fill up your 160 MB/s bus. > Naively, I was under the impression that only because of striping that > Gb/s flux could be achieved, but you say that a single disk can w/r > with 160 MB/s? Striping is needed. And this will work for specific IO patterns. Random I/O (reads and writes) on small blocks is usually the pathological case for a fast file system hardware/software design. Large block sequential sustained reads are the optimal case. The folks doing database testing like to talk about disks in terms of Op/s, the number of operations per second. -- Joseph Landman, Ph.D. Senior Scientist, MSC Software High Performance Computing email : joe.landman@mscsoftware.com messaging : page_joe@mschpc.dtw.macsch.com Main office : +1 248 208 3312 Cell phone : +1 734 612 4615 Fax : +1 714 784 3774