Performance problems with new disks

[Daniel Schneider]

Hi all,
we have a big problem with a K370-Machine, who has been extended with two hard disks.
All available disks are mirrored, so that from the two new disks one is data and the other is mirror.
The Server is running with oracle and after the installation of the new disks, the system is very slow on the new disk.
We have tested it with copying a file from about 150Mb.
To copy this file on the new disk runs for about the double time as the same process on the old disks.
Extended Disks are build in a "HASS"-System.

The new disks are attached at the end of the SCSI-Bus. So there are old disks on this bus, who enclose some oracle data which is very often used, and the new ones with oracle data too.

Are there any ideas for the reason?
Is there some experience with problems in a "HASS"-System?
Could the problem derive from the fact that the disks with the lower SCSI-ID than the new ones are very heavy used?

Thanks for all help!

Best Regards
Daniel :-)

[Stefan Farrelly]

What are the model of disks ? Use the diskinfo command to display the model. From that I have a table of performance for all these disks and can tell you how fast they are. All these tests were done using raw dd on the disk (sending output to /dev/null)

[Xavier Gutierrez]

Hi, Daniel

The thing you point in your message is absolutely correct: it could be because the disks with the lower SCSI ids are heavily used. Anyway, could you please send us an ioscan of your machine?

Regards.