I had mentioned a lot of this in another LR thread a few weeks ago, but the history is a bit important to the new information so I'll try and be brief.
System, i7-920 @3.80ghz, 12g RAM, (2) 5770 video cards, etc.. so a fairly quick desktop. The LR cache is 100gigs and on the index/preview drive.
I wanted to experiment with increasing my preview speed(s) by putting the indexes/previews on their own drives and I tried several different combinations with these results.
In excess of 100,000+ mostly raw images on 3 year old 1tb drive. It took a good second or two for the image to fully render.. noticeably slow when moving to a new folder or collection.
I put about 10,000 images and 1:1 previews on a Crucial C300 256gb SSD via SATA3.. this is currently the fastest overall SSD in SATA format so I wanted to use it as a baseline. Images rendered 'instantly' and moving between folders and collections was instant as well. Obviously this is the desired result but way too expensive for the size I need for my full catalog.
I then moved the entire 100,000+ images to a six month old 2tb drive.. sequential write/read speeds in excess of 100mbps.. Performance was very good but it wasn't a SSD. About a second between folders/collections.. but once there, there is a slight pause between fully rendering each image. This is a fast 2tb drive.. the catalog was optimized, probably to date the best overall solution for the cost. Dedicating a fast HDD just for indexes/previews/cache.. is definitely the way to go for cost/value/performance.
New information: I had ordered (2) Seagate Momentus Hybrid 500g 2.5 inch (laptop width) drives and they came in today. I placed 20,000 images and built a new index and 1:1 previews on one of these.. and used it for ten minutes or so going through different folders/collections, back again, then going to an entirely new folder, back again..
As you know the SSD portion of this hybrid is read only and it's optimized to quickly learn your latest accesses.. Performance on first access was equal to or slightly exceeding the fast 2tb drive above. Second access was faster, third access was noticeably quicker. Not Crucial C300 full on SSD fast.. but significantly faster than the fast 2tb mechanical drive.
The problem for me is that while the price is reasonable ($124 for a 500g hybrid) its just not big enough for my full catalog. So.. I put both hybrids in the system and spanned them, built indexes/1:1 previews for about 60,000+ images.. and gave it a go.
Surprisingly (or maybe it shouldn't have been) performance was below that of the older 1tb drive.. probably what you would expect for a 7200rpm notebook drive.
I'm guessing the programming for the SSD read portion is being disabled in a spanned drive.. or at a minimum is getting mixed up. I'm not sure if running them in a RAID would have the same results.. I suspect it would. Normally if you put two SSD's in a RAID the performance increase is stunning.. but with the hybrids I doubt it would be.
I'm back to the fast 2tb drive as a standalone for my entire catalogs indexes/previews/cache.. but now I'm thinking what if.. what if I put the cache on a standalone inexpensive SSD like the X-25v 40g.. while leaving the indexes/previews on the fast 2tb drive.. Or the cache on one of the hybrids..
I suppose in a few years we'll be laughing at all this and our 50tb bus accessed SSD's will be moving at light speed.. but for now the faster access times and reducing the 'hang' time between folders/collections and rendering a full 1:1 preview can sure enhance the experience..
Btw.. I have a C300 256gb SSD in my x201s Thinkpad.. and LR3 and CS5 are both silly fast for a notebook.. if your needs are along these lines I consider the SSD an excellent value.
