SCSI harddisk performance in XP

[VJ]

Hello,

I'm experiencing a strange issue with my computer. I'm using 2 10K SCSI drives (Seagate Cheetah 10k.6, IBM Ultrastar 36lzx), connected to the onboard SCSI controller of a Supermicro X5DA8 on an XP Pro box. It is known there are issues with the SCSI implementation on XP ( http://forums.storagereview.net/inde...showtopic=7228 ).

Now, I'm trying to find out if my system performs as expected. I ran the virtualdub benchmark (in auxsetup.exe). These are the results for the IBM:

1. Windowsbuffer enabled (checkbox unchecked, default)
peak disk performance (50 MB)
sustained read: 544681 KB/s
sutanined write: 8512 KB/s

videocapture performance:
640x480x16
200 frames
50 buffers
FPS = 25.000
(yields a datarate of 15000)

=> 12 % dropped frames


2. Windowsbuffer disabled (checkbox checked)
peak disk performance (50 MB)
sustained read: 18510 KB/s
sutanined write: 19738 KB/s

videocapture performance:
640x480x16
200 frames
50 buffers
FPS = 25.000
(yields a datarate of 15000)

=> 0 dropped frames

I then tried with XP Cachefilter (got it from Storagereview):

This program installs a small filter driver, which clears the FUA (Force
Unit Access) bit from SCSI write commands. This has the potential to
improve write performance, at the expense of greater risk in the case of
disk or power failure.

1. windows buffering enabled
peak disk performance (50 MB)
sustained read: 465455 KB/s
sutanined write: 21843 KB/s

2. windows buffering disabled
peak disk performance (50 MB)
sustained read: 18208 KB/s
sutanined write: 28240 KB/s

Both cases yield 0 dropped frames



The differences are similar when benchmarking the Seagate (without windowsbuffering and with the XP Cachefilter, it claims a writespeed of about 54000 KB/s ! )

Does anyone have experience with this XP Cachefilter Tool ? How big is the impact regarding possible dataloss ?
(should I get me a UPS ? )

My system seems to perform better without the Windowsbuffers. Are there ways to disable it to give me better write performance in Windows overall ? Or are there reasons not to do this ? Does it perhaps have tweakable settings ?

What else can I do to get proper results ?


Thanks!


Jörg

[Gurm]

When they say "possible data loss" they mean "covering our ass".

The data loss potential is the same as it would be under any other operating system.

XP just "plays it safe" at the expense of performance.

At least, that's my understanding of the situation. Having abandoned SCSI some time ago due to rising costs with diminishing returns, I no longer have a vested interest in figuring it out further.

- Gurm

[VJ]

Yes...

The XP Cachefilter only improves on write speed, increasing it by 10 MB/s; disabling the Windowsbuffers increases write speed by another 10 MB/s (read performance seems incorrect )

So, that partly confirms the reason for XP Cachefilter.

Still, I wonder what that Windowsbuffer is... Is it something Virtualdub generates ? Or is it used in 'normal' Windows operations (file copy, ...) ? How come it makes write performance so bad ?


Jörg

[Gurm]

I think it's something VDub makes, to be honest.

- Gurm