This post is from a 3Ware representative:
"I looked into the benchmark results, and I found out why the 3ware Escalade
card performed below expectations in the ATTO Bench32.exe benchmark results.
When the Bench32.exe program runs in Direct I/O mode (i.e. the Direct I/O
box is checked in the Bench32.exe program, which is the default), then all
writes to the disk drive are sent with the FUA bit set (when Windows basic
disks are used). FUA stands for Force Unit Access, and is defined for SCSI
devices. The 3ware Escalade card, Adaptec 2400A, and the HighPoint
RocketRAID card all appear as 'SCSI and RAID controllers' to Windows 2000.
The FUA bit is a way that a computer program can ensure that data is written
to the physical medium of the disk drive, and not just cache memory before
it is acknowledged.
Here is the definition from the SCSI spec, on page 15 of Information
Technology - SCSI Block Commands - 2 (SBC-2), Revision 4 dated 28 July 2001:
"Sometimes the application client may want to have the blocks of data read
from the medium
instead of from the cache memory. The force unit access (FUA) bit is used to
indicate that the
device server shall access the physical medium. For a write operation,
setting FUA to one causes
the device server to complete the data write to the physical medium before
When Bench32.exe is run on a Windows 2000 basic disk, with the Direct I/O
box checked, all writes to the disk drive are done with the FUA bit set.
The 3ware controller honors this bit, and sends a flush command to the disk
drive after every write to ensure that the data is truly written to disk.
That is why the 3ware card shows lower numbers. Even though the Adaptec
2400A and HighPoint RocketRAID cards receive the write command with the FUA
bit set, they do not send the flush command to the disk drive. This can
easily be verified using an ATA bus analyzer.
When Bench32.exe is run on a Windows 2000 dynamic disk, then the FUA bit is
not set when using Bench32.exe. As you can see from the benchmark results,
this results in much better performance for the 3ware controller."
3ware Inside Sales Manager