在aix系统上，大家都知道打开iostat历史信息收集对系统性能有影响，但是影响到底有多大呢？

首先检查lsattr -El sys0|grep iostat

lsattr">lsattr -El sys0|grep iostat
iostat false Continuously maintain DISK I/O history True

在关闭模式下，用filemon捕获结果如下(部分)

VOLUME: /dev/alisoft_8g_329 description: raw
reads: 8093 (0 errs)
read sizes (blks): avg 16.0 min 16 max 16 sdev 0.0
read times (msec): avg 136.945 min 8.211 max 1202.791 sdev 67.955
read sequences: 7861
read seq. lengths: avg 16.5 min 16 max 80 sdev 4.3
writes: 565 (0 errs)
write sizes (blks): avg 16.0 min 16 max 16 sdev 0.0
write times (msec): avg 157.580 min 0.237 max 578.688 sdev 116.360
write sequences: 564
write seq. lengths: avg 16.0 min 16 max 32 sdev 0.7
seeks: 8425 (97.3%)
seek dist (blks): init 2901536,
avg 1570417.3 min 16 max 16255456 sdev 3023224.7
time to next req(msec): avg 15.927 min 0.000 max 3050.591 sdev 84.087
throughput: 502.3 KB/sec
utilization: 0.75

在iostat打开模式下,filemon报告如下(部分)：

VOLUME: /dev/alisoft_8g_329 description: raw

Reads: 7441 (0 errs)
read sizes (blks): avg 16.0 min 16 max 16 sdev 0.0
read times (msec): avg 132.014 min 7.203 max 603.592 sdev 57.236
read sequences: 7181
read seq. lengths: avg 16.6 min 16 max 80 sdev 4.6
writes: 1637 (0 errs)
write sizes (blks): avg 16.0 min 16 max 16 sdev 0.0
write times (msec): avg 343.068 min 0.235 max 663.595 sdev 198.932
write sequences: 1632
write seq. lengths: avg 16.0 min 16 max 32 sdev 0.9
seeks: 8813 (97.1%)
seek dist (blks): init 3346304,
avg 1929239.9 min 16 max 15460208 sdev 3273629.5
time to next req(msec): avg 12.818 min 0.000 max 1390.868 sdev 61.882
throughput: 624.1 KB/sec
utilization: 0.74

从这里可以看出，iostat历史信息打开对写的响应时间影响还是较大的。

ps:

这里面有个bug。在系统安装好后，iostat默认是关闭的，此时topas里面是能够看到hdisk的繁忙程度的。但是一旦我们去打开它，再去关掉它的话，在topas里面hdisk的繁忙程度就看不到了。真是晕死。。。