MacOSG: MacOS X is having trouble handling SSD hard drive speeds (update)
"Mac OS X has an issue with couple of things, and this was bound to happen -- the Apple-written SATA controller driver can get saturated by a single SSD drive on ocassion, but two will definitely saturate the bus. The underlying issue is the fact that Mac OS X comes with journaling filesystem, a feature not present on Windows-based file systems.
"The only way to avoid this is by buying an external RAID controller that comes with its own drivers, independent of the built-in SATA drivers. Now, brace for impact - upcoming Mac OSX Snow Leopard WILL NOT fix this one in its initial release, we will have to wait for an Apple Update, if it ever comes out. The issue is present in all Mac OS X releases with SATA drive support, so you lose 10MB/s if you use a very fast SSD drive."
If you plan on putting a SSD drive in your Mac laptop down the road, and until Apple modifies Mac OS X, make sure the drive is compatible or you could run into saturation problems. OCZ makes special SSD Mac drives that are slowed down by 10MB/s in order to avoid saturation on the software side.
UPDATE: Apple released a MacBook Pro EFI Firmware Update. Apple states, "MacBook Pro EFI Firmware Update 1.7 addresses an issue reported by a small number of customers using drives based on the SATA 3Gbps specification with the June 2009 MacBook Pro. While this update allows drives to use transfer rates greater than 1.5Gbps, Apple has not qualified or offered these drives for Mac notebooks and their use is unsupported."