PERFMON - Percent Idle Time (disk) 1

[Ovatvvon]

Hi Everyone,

For anyone who's used PerfMon (at least on Windows 2003):

I used it to collect performance data while users pounded the database. The results came back a bit funny for the % Idle Time counter though.

In several cases, the MAX value for all counters was above 100%. In fact, it wasn't even a tiny bit above 100%, but it would give a number like "21865.4" <-- That's an actual value received.

Does anyone know how this could be, or what exactly that means?





-Ovatvvon :-Q

 

[mrdenny]

Quite a few of those % Idle values are worthless as they are a funky average, so the numbers can be all over the place. Pay more attention to the IOs per second, and seconds per read and seconds per write.

Denny
MVP
MCSA (2003) / MCDBA (SQL 2000)
MCTS (SQL 2005 / SQL 2005 BI / SQL 2008 DBA / SQL 2008 DBD / SQL 2008 BI / MWSS 3.0: Configuration / MOSS 2007: Configuration)
MCITP (SQL 2005 DBA / SQL 2008 DBA / SQL 2005 DBD / SQL 2008 DBD / SQL 2005 BI / SQL 2008 BI)

My Blog

 

[Ovatvvon]

Ok. I have been using avg. sec/read & write all along. Microsoft recommended % idle time too, which is the only reason I included it, but it seems, like you said, worthless.

Any idea what IO's / second should look like, both for DAS and SAN? (i.e. non-cached vs. cached, and I/O's per spindle)?


-Ovatvvon :-Q

 

[mrdenny]

IOs / second will totally depend on your database load. Low load systems will have a very low number. High load systems which are mostly read, but have a high page life expectancy will have a low number. High write systems will have low numbers, until a checkpoint hits then some massive numbers.

Most spindles can handle about 400 IOs per second for random IO patterns. That number goes up a lot for sequential IO patterns such as a data warehouse.

Denny
MVP
MCSA (2003) / MCDBA (SQL 2000)
MCTS (SQL 2005 / SQL 2005 BI / SQL 2008 DBA / SQL 2008 DBD / SQL 2008 BI / MWSS 3.0: Configuration / MOSS 2007: Configuration)
MCITP (SQL 2005 DBA / SQL 2008 DBA / SQL 2005 DBD / SQL 2008 DBD / SQL 2005 BI / SQL 2008 BI)

My Blog