Slower MySQL inserts for AMD64/Opteron?

[David O'Brien]

On Wed, Jun 22, 2005 at 10:41:59AM -0700, ray at redshift.com wrote:
> I did some benchmarks recently on a single 2.4Ghz Xeon against a Dual
> 246 Opteron and noticed when it came to MySQL inserts, the single Xeon
> was about 20% faster on inserts (and it actually had a slower hard
> drive, IDE vs SATA).  The interesting thing is that the Dual Opterons
> was twice as fast retrieving the data using selects.
..
> The Xeon was running 5.3/i386.  I believe the AMD was running 5.4/AMD64.

Note that in 5.4, the ATA subsystem runs without the Big-GIANT-Lock.  CAM
(SCSI subsystem) still grabs GIANT.  For a system with a single activity
going on (such as yours), I feel ATA can "out perform" SCSI doing some
things.  Note that most IDE disks lie and always cache things.  If MySQL
is doing fsync's to ensure the data is on disk, the ATA disks can seem
faster, but aren't as save and reliable than SCSI disks.  There are many
reasons one uses SCSI over IDE disks.  "Raw" performance isn't
necessarily one of them.

Summary: please try an IDE disk in the Opteron machine.  Preferable pull
the disk out of the Xeon, put it in the Opteron and re-run your
benchmark.

-- 
-- David  (obrien at FreeBSD.org)