Is it possible to install an SSD in the Mac Pro models instead of a hard drive? How does this impact performance?

Apple does not offer an SSD option for the Mac Pro -- only for MacBook Pro models -- and Solid State Drives are more commonly desired for portable systems.

However, if you can figure out a way to adequately secure a 2.5" SSD in one of the 3.5" Mac Pro drive bays, it is quite possible to install just about any SSD in a Mac Pro provided that the SSD is compatible with a 3Gb/s Serial ATA connection.

Photo Credit: AnandTech (Hanging SSD in Mac Pro)

First noting that the author assumes "you're good with metal (or rubber bands) [and] you'll find a way to get the drive in there", the always excellent AnandTech installed an Intel X25-M SSD in both the original Mac Pro "Eight Core" 3.0 and the Mac Pro "Eight Core" 2.26 (Early 2009/Nehalem) models, and unsurprisingly found that replacing the slower hard drive with a faster SSD made a significant difference in the performance of drive-related tasks.

In one particular test -- performing a processor-intensive compile for a development project -- AnandTech reported:

With a standard 7200 RPM hard drive, the new Nehalem Mac Pro is nearly 24% faster than the original 8-core Mac Pro. However, swap in Intel’s X25-M and the new Mac Pro is almost 30% faster. . .

The explanation is simple. Nehalem is more data hungry than any previous generation Intel microprocessor. It can operate on twice as many threads as Penryn and Conroe and it has much deeper buffers internally. To fill them with instructions it needs fast access to memory, which it has. Unfortunately not everything you ask of it is already in memory, and that's where the burden gets pushed down to the hard drive. Speed up the hard drive and you'll help Nehalem shine.

Ultimately, apart from physically securing the drive, it is quite simple to install an SSD in a Mac Pro -- and the performance difference for drive-related tasks is significant. Whether or not the extra performance of an SSD is worth the extra price compared to a hard drive is up to you.