From: Haessner, Roland (Roland.Haessner@t-systems.com)
Date: Mon Jul 15 2002 - 02:56:23 EDT
> Hi admins :-)
>
> I have a question to you :
> We are using an oracle8 database, HPUX 11i, a L-Cass server (2 CPU, 4GB
> RAM) and a VA7100 as storage system, connected via two brocade switches.
> When we are using a dd-command from /dev/zero to the LUN's (50 MB file),
> we get different time values :
>
> - with a blocksize of 1024 (bs=1024) it needs about 2 seconds ... that's
> okay
>
> - with a blocksize of 1000 (bs=1000) it needs about 40 seconds !
>
> That's crazy, isn't it ? A similar behaviour shows the tar-command.
>
> To analyse the performance and for understanding the optimal parameter
> values for buffer cache, kernel parameter and other io specific parameters
> i would like to know more about the way of IO ... from the application
> down to the disks !
>
> Are there any whitepapers, overviews or descriptions about this way of IO,
> about main parameters ?
> Do you know where this big difference comes from ? Why is this blocksize
> soooo impotant ? How can i check the values of these parameters ?
>
> Thanks for all answers to my mail, i will summarize as soon as possible !
> Roland
> :-)
>
> roland.haessner@t-systems.com
>
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