The following is a demonstration of the iopattern program,

Here we run iopattern for a few seconds then hit Ctrl-C. There is a "dd"

command running on this system to intentionally create heavy sequential

disk activity,

# iopattern

%RAN %SEQ COUNT MIN MAX AVG KR KW

1 99 465 4096 57344 52992 23916 148

0 100 556 57344 57344 57344 31136 0

0 100 634 57344 57344 57344 35504 0

6 94 554 512 57344 54034 29184 49

0 100 489 57344 57344 57344 27384 0

21 79 568 4096 57344 46188 25576 44

4 96 431 4096 57344 56118 23620 0

^C

In the above output we can see that the disk activity is mostly sequential.

The disks are also pulling around 30 Mb during each sample, with a large

average event size.

The following demonstrates iopattern while running a "find" command to

cause random disk activity,

# iopattern

%RAN %SEQ COUNT MIN MAX AVG KR KW

86 14 400 1024 8192 1543 603 0

81 19 455 1024 8192 1606 714 0

89 11 469 512 8192 1854 550 299

83 17 463 1024 8192 1782 806 0

87 13 394 1024 8192 1551 597 0

85 15 348 512 57344 2835 808 155

91 9 513 512 47616 2812 570 839

76 24 317 512 35840 3755 562 600

^C

In the above output, we can see from the percentages that the disk events

were mostly random. We can also see that the average event size is small -

which makes sense if we are reading through many directory files.

iopattern has options. Here we print timestamps "-v" and measure every 10

seconds,

# iopattern -v 10

TIME %RAN %SEQ COUNT MIN MAX AVG KR KW

2005 Jul 25 20:40:55 97 3 33 512 8192 1163 8 29

2005 Jul 25 20:41:05 0 0 0 0 0 0 0 0

2005 Jul 25 20:41:15 84 16 6 512 11776 5973 22 13

2005 Jul 25 20:41:25 100 0 26 512 8192 1496 8 30

2005 Jul 25 20:41:35 0 0 0 0 0 0 0 0

^C