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Re: improving i/o performance and max depth queue diskes with slow users

 
Max5
Occasional Advisor

Re: improving i/o performance and max depth queue diskes with slow users

this is the bottleneck, for exemple , just 2 rows is visible ..  some 100 % cpu's (not all)

and avwait values 59 or 54 > then avserv values 8 or 7 ... 

disk07 99.80 55.19 936 111218 59.88 8.52

c3t2d0 100.00 53.28 1016 121446 53.22 7.85

 

sorry for the few exemples.

Bill Hassell
Honored Contributor

Re: improving i/o performance and max depth queue diskes with slow users

...sorry for the few exemples....

Analyzing and resolving performance concerns requires a lot of measuremnts and information about what is using the system resources. There is no magic switch or parameter to make your system run faster. You can make any disk 100%  busy with the dd command, or make all the CPUs busy with a simple script. The application (database perhaps) is causing the load. Stop the application and performance will be excellent.

Is the application something that can be changed, perhaps rewritten to be more efficient?

The latest measurement shows two different disks that are very busy. The queue depth for both disks is over 50, so changing the SCSI driver depth to 32 will produce no change for that specific moment in time. 

Changes for various parameters are meaningless if you do not have a repeatable load. For this simple example, you would have to change all your external disks for solid-state disks. In that case, you would see immediate performance gains.



Bill Hassell, sysadmin