IDE software RAID5 write performance

NTDEV
1

Why is Windows 2000/2003 RAID5 write performance so low?

The test system:
Athlon 2000 MHz, 66 MHz/64 bit PCI, IOAPIC, software RAID5 volume made from
6 recent 7200 RPM IDE drives on 3 IDE controllers.

Read bandwidth: Windows and Linux 2.4 – about 140 MB/s
Write bandwidth: Linux 2.4 – about 110 MB/s, Windows – about 35 MB/s, CPU
is not maxed out.

Dmitriy Budko, VMware

2

> Why is Windows 2000/2003 RAID5 write performance so low?

The test system:
Athlon 2000 MHz, 66 MHz/64 bit PCI, IOAPIC, software RAID5 volume made
from
6 recent 7200 RPM IDE drives on 3 IDE controllers.

Read bandwidth: Windows and Linux 2.4 – about 140 MB/s
Write bandwidth: Linux 2.4 – about 110 MB/s, Windows – about 35 MB/s,
CPU
is not maxed out.

Well. I havent seen the driver.
But that smells like Linux is doing “write-multiple-sectors, update parity
once” optimization and Windows is not.
But again, I havent seen the driver so I’m just guessing.

Regards,

Paul Groke