Found this transcript of a Maximum PC article from September:
SCSI Slowdown
Your hard drive performance may be slower than you'd expect if you're running
Windows XP Professional or Home with a SCSI rig. That's what users of
high-priced and supposedly high-performance SCSI equipment are apparently
finding as they convert to Windows XP Pro or Home from Windows 2000 or 98. In
fact, Maximum PCs own crew ran into the XP/SCSI bug this month when they first
laid down the configuration for the Dream Machine (see page 24). Instead of the
nice-but-not-so-exotic ATA RAID configuration that ended up in this year's dream
rig, the original configuration included a new hot-to-trot Seagate Cheetah 15K.3
drive. Packing 73.4GB of storage capacity 3.6ms seek times, and a 15,000 spindle
speed, the Cheetah may well be the fastest hard drive around end can even motor
past an ATA RAID configuration without breaking a sweat. Indeed, using the
quick-and-dirty ATTO hard drive benchmark under Windows 2000 Professional, the
Cheetah 15K.3 can't be beat by anything in read or write speeds. Run the drive
with Windows XP Professional however, and the Cheetah 15K.3 is outperformed by a
5400rpm budget drive in write speeds of small files. The problem isn't Seagate's
new wonder drive - it's an incompatibility between Windows XP Professional and
certain disk intensive applications.
Only at hard drive fetish web sites such as Storagereview.com has the problem
begun boiling over as forum members search for solutions. A previous NTFS fix
doesn't solve the problem, nor does the upcoming Service Pack 1. But don't start
selling your equipment on eBay, just yet. The Dog has learned from Microsoft
that a fix is on the way.
Jeff Goldner, a development manager for the Windows-based group, told The Dog
that a combination of long-term goofs led to the SCSI slowdown.
"We share some blame here. Goldner said "[with previous OS versions], we told
developer to set FILE_FLAG WRITE_THROUGH and FILE FLAG_NO_BUFFERING to obtain
better performance." Unfortunately, these instructions don't jibe with Windows
XP.
Goldner said the problem actually existed under Windows 2000 too, but many users
probably wouldn't have noticed it without turning off write caching. Under
Windows XP, the problem manifests because it's assumed by Microsoft that the
write through setting is not being used by the application. But because of
previous encouragement by Microsoft, many applications that stress the hard
drive (such as DV, AV, and benchmark tests) request the flag nonetheless.
"We've dune some tests and have seen up to 10x performance hits depending on the
packet size, Goldner said. "It depends on the drives and how they implement the
cache." Unfortunately, the flag cannot simply be removed from XP because its
absence can affect file integrity. Much of the problem can be addressed by
recompiling the applications with the flag turned oft or by using XP's
compatibility update feature. The updates can fool the applications into
thinking the flag is on, while actually switching it off. Goldner said Microsoft
expects to release updates within the next three months and will also issue a
more detailed Knowledge Base item. Woof.
