whether to install an mSATA or not for Photoshop/Lightroom usage

I have my 5D up and running with 5 3TB Toshiba PH3300U-1I72 hard drives and so far it’s great. I’m going to primarily be using this drive with Photoshop and Lightroom, and as cold storage for old projects that I no longer need on my desktop, and maybe as the scratch disk drive for Photoshop.

I’ve done plenty of reading on the usefulness of adding an mSATA drive for the cache when using Photoshop and Lightroom, but I’m interested in hearing if those that have added an mSATA drive this feel that it’s worthy upgrade. Since buying the Drobo and 5 drives has left my wallet a little thin, I’m being a little stingy with adding the mSATA card.

The Photoshop files that I work with on the Drobo are usually under 3GB in size, and I’m keeping the Lightroom catalog file on the internal hard drive, and using the Drobo for storage of the actual raw files.

For reference, these are the speeds I’m getting over Thunderbolt from AJA System Test:

     File Size Sweep

MB MB/sec
Read Write
128.0 257.5 330.9
256.0 244.2 320.9
512.0 295.1 288.2
1024.0 392.7 261.3
2048.0 414.2 251.6
4096.0 348.9 250.3
8192.0 349.9 251.7
16384.0 350.6 247.4