Volume Manager - Striping -> sequence writing performance

Typical setup of a Oracle database server could be:

Systemdisk mirrored.

10 disks striped and mirrored as RAID 0+1 for the database-volume.

I have used the command: "time mkfile 1000m testfile" to test the sequence write performance. I wonder why I get performance of c.a. 60 sek when I write to the systemdisk (one mirrored disk), but only c.a. 38 sek when I write to the database-volume (5 striped disks mirrored with 5 other) !?

Why don't I get c.a. 4-5 times performance increase (c.a. 13-15 sek) ?

Do you have the same sindrome on your servers ?

Is this normal and then why ?

Regards

Halldor Gretar

p.s.

This sindrome is on all servers that I have tested, both setup by me and others, and both with Veritas Volume Manager and Sun DiskSuite.

[820 byte] By [hge1] at [2007-11-25 23:11:54]