[ILUG] Poor Bonnie results ?

[Niall O Broin]

I was doing some testing on a big box which inspired me to run bonnie on the
disks on my desktop machine. I tested two IDE disks and a SCSI disk with the
following results:

              ---Sequential Output (nosync)--- ---Sequential Input-- --Rnd Seek-
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --04k (03)-
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU   /sec %CPU
hdb    1*1500  5033 54.0  6124  6.2  3239  4.3  8571 80.8  9544  4.8   67.2  1.2

              ---Sequential Output (nosync)--- ---Sequential Input-- --Rnd Seek-
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --04k (03)-
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU   /sec %CPU
hda    1*1500  4459 68.2  7080 21.3  3400 49.3  4363 75.6  7639 73.9   70.0  8.1

              ---Sequential Output (nosync)--- ---Sequential Input-- --Rnd Seek-
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --04k (03)-
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU   /sec %CPU
sda    1* 500  5263 56.1  4524  4.7  2212  2.9  3856 35.8  4292  2.4   66.3  0.8

Both IDE disks had been tuned with hdparm -c 1 -m 16. I don't know where on the
curve the sequential I/O figures lie but the random seek figures on the IDE
drives and the SCSI drive are atrocious, at least by comparison to the big box
I'm testing which looks like this

              ---Sequential Output (nosync)--- ---Sequential Input-- --Rnd Seek-
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --04k (03)-
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU   /sec %CPU
pogo   1*1500  6706 47.1  7297  3.9  3391  2.7  6039 43.9 79283 30.0  862.5  5.8

and the figures recently posted by John Ronan for a box with 2 x PIII 933,
1GB Ram, 2.2.19smp kernel, SmartArray 3200 with 64MB

              -------Sequential Output-------- ---Sequential Input-- --Random-Seeks
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block---

Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
m1       1500  8726 65.7  9331  5.2  5740  8.4  9482 65.9 57447 30.9 785.8  7.7
 

The big box has a bit more oomph (2 X 1G PIII, 1G RAM, 425 GB IDE RAID-5) than
my desktop (750MHz Athlon, 256M RAM) but even so, they seem like miserable
random seek figures. I just ran the test on my notebook (700MHz PIII,  192M
RAM) and got

              ---Sequential Output (nosync)--- ---Sequential Input-- --Rnd Seek-
	      -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --04k (03)-
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU   /sec %CPU
bilbo  1* 500  4476 93.9  6281 54.1  3066 70.5  4414 86.2  6349 66.9   76.3  6.3

which is in the same order, seek wise,  as the disks on the desktop. Is
there something I don't know about RAID-5 subsystems which makes them
stunning performers on random seek. They should be quite good for block
input, as mine and John's figures show, but why random seek ?


Regards,


Niall