andrew@alice.UUCP (Andrew Hume) (03/29/90)
we bought a second smd disk controller for our 4D/240 and (of course) tried to measure how much better things were. the times are given below. the question is, why does the i/o speed go DOWN as the buffer size increases for the case of inter-controller i/o? andrew hume (andrew@research.att.com) --------------------------------------------------------- timing tests for i/o through the file system (efs) on a 4D/240 with 2 Xylogics 754 controllers and Sabre disks. these show clock seconds for copying a 40MB file 1) on a single disk, 2) between two disks on the same controller, and 3) between disks on different controllers. c1d1->c1d1 c1d1->c1d3 c1d1->c2d0 cp 100 73 26 dd bs=4k 98 73 26 dd bs=8k 98 74 25 dd bs=16k 97 73 25 dd bs=64k 66 54 28 dd bs=125k 58 51 29 dd bs=500k 51 48 31 dd bs=2000k 47 44 40 times seem accurate to +- 1s. buffer pool flushed between trials. (average of 3 single-user runs.)