On 6/23/06, Richard Elling <[EMAIL PROTECTED]> wrote:
comment on analysis below...
Tao Chen wrote:
> === Top 5 Devices with largest number of I/Os ===
>
> DEVICE READ AVG.ms MB WRITE AVG.ms MB IOs SEEK
> ------- ------- ------ ------ ------- ------ ------ ------- ----
> sd1 6 0.34 0 4948 387.88 413 4954 0%
> sd2 6 0.25 0 4230 387.07 405 4236 0%
> cmdk0 23 8.11 0 152 0.84 0 175 10%
>
>
> Average response time of > 300ms is bad.
Average is totally useless with this sort of a distribution.
I'd suggest using a statistical package to explore the distribution.
Just a few 3-second latencies will skew the average quite a lot.
-- richard
A summary report is nothing more than an indication of issues, or non-issue.
So I agree that an "average" is just, an average.
However, "a few 3-second latencies" will not spoil the result too much when there're more than 4000 I/Os sampled.
The script saves the "raw" data in a .rec file, so you can run whatever statistic tool you have against it. I am currently more worried about how accurate and useful the raw data is, which is generated from a DTrace command in it.
The "raw" record is in this format:
- Timestamp(sec.microsec)
- DeviceName
- W/R
- BLK_NO (offset)
- BLK_CNT (I/O size)
- IO_Time (I/O elapsed time)
Tao
( msec.xx)
Tao
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