Tr, while our disk subsystems may be similar, our processors are most definitely not. Nor, I suspect, are our mother boards even in the same ballpark. I have the last of the last generation of the Core 2 technology and you have the first of the Core i7 technology. Believe me; these systems are as different as night and day. Your 12GB is DDR 3, my 8GB is DDR2; your controllers are SATA 3 and while my disks are SATA 3, my controllers are SATA 2; your USB is 3, mine is 2; you have built in Turbo over clocking, raising your processor speed to 3.46 Ghz, I have no Turbo capability at all. This list could go on for every sub-component, but trust me when I say your system is quite likely the new MINIMUM system configuration for heavy LR users.
I have solved my fragmenting problem by using Perfect Disk to avoid fragments in the first place but that has no bearing on why I separated my working datasets. I did that to avoid contention for the channel controllers during multiply processor access. The big culprits were the LR cache and system page file; you saw the contention effect that occurred when I ran my speed tests concurrently. The page file is of particular concern because LR memory demand will grow to 3-3.5GB if I am very active in switching between the various modes such as Library, Develop and Slideshow during a long editing session. Further, the cache can be very active during rendering and preview generation, so when LR has gotten big enough to cause paging and LR is hitting the cache heavy, well you know the rest of that story. To make matters worse, I have a 1GB graphics card that can consume 4GB of main memory during its rendering process thus driving paging even higher. I watched the access times on my page file creep up to as much as 35ms!! It should be 0 to1 ms, tops.
I didn’t mention this before, but I am a novice LR user, I purchased it on February 25th of this year. I am self taught using The Adobe Photoshop Lightroom 4 Book for Digital Photographers by Scott Kelby. I spend a lot of time doing and undoing stuff to see how it works. I believe that was the reason my file system became a fragmenting problem. I don’t know what I was doing to cause any of the files to grow enough to cause it to fragment, but I’m certain that something like preset history, which can grow fast, is at the heart of the matter; I’m my own worse enemy. I suspect that whatever you do doesn’t cause much fragmentation. One note here, you mentioned that you have only 1% fragmentation in your Catalog, Previews, and Camera Raw Cache partition. It’s more important to know which files are fragmented than to know what percentage is fragmented. If, as was my case, your catalogue is heavily fragmented you will have problems each time you access it. Believe it or not, my page file has even gotten fragmented! So you need to use a product like Perfect Disk to analyze each and every file (geez, I sound like a Perfect Disk salesman LOL).
I think that the heart of the matter is that digital photography software (Photoshop, Lightroom, etc) has driven older general purpose technology platforms past their useful lives. I’ve determined that my system is about as good as it can get and I’ve done everything financially reasonable to make it better. I suspect many others may eventually come to that conclusion. I think I have learned enough that I could spec out a LR specific system that would be pretty nearly bullet proof. Adobe would be wise to work with Dell, HP or even Apple to configure a special Lightroom Edition PC. Sorta like a Saleen Edition Ford Mustang.
Bill