Can I slim down the size of the Aperture Library by moving the Preview files elsewhere?

Question

Hi all,
I have an Aperture library of almost 20,000 photos, dating back to around 2007. Almost all the master images are stored on an external drive (backed up of course), with only my recent and 'in progress' masters being stored in the library itself. Previously I have had my library split up into one library for each year, with the older years libraries being stored on the external drive where the masters are, in order to keep the size of my 'current' library down. So my current library, stored on my internal SSD, contained only photos from this year and last year, and only a few of the masters for these images. Confusing? Sorry!
Now, I recently decided to consolidate the libraries into one huge library, because it was annoying to have to switch between libraries to find older photos when I wanted them. I did this, leaving all but the recent masters on the external drives (referenced). I thought that the size of the main library would remain reasonably sized, since there were no extra masters being moved into it. However, the library has grown massively - up to over 70GB, which is huge when you consider it's on a 128GB SSD which is also my startup drive.
I'm pretty certain the reason for the huge size increase is that the Previews for all the older images are stored in the Library file, rather than anywhere else. This makes sense - they are previews, they're supposed to be able to be viewed with the external drives disconnected. So my question is this. Am I able to change the location of the preview files to be on my OTHER internal hard drive (non-SSD, much larger), so that they're still available without the external drives, but are not cluttering up my startup drive. And, if not, what should I do!?
Thanks a lot

Answer 1

Glad it worked, but permit, if you will, some observations:
-- Bloated Previews are a known Aperture bug, which came and went  within a few updates in Aperture 3. Getting them back to the proper size is simply a elegant step to take.
-- A Preview set to your largest screen size and a quality of 6-8 should be all but indistinguishable from the Master at 72-100 dpi screen image. (Not print resolution.) I REALLY doubt you are going to loose any quality.
-- While using a symlink to stick the Previews on a HD is clever, it may also defeat the whole purpose of using your SSD. Previews are read a lot and are, I suspect, used for all adjustments at less than full resolution. (N.B. I could be VERY wrong on this.) Thus, depending on the amount of RAM on your Mac, you could end up reading and rereading your Previews over a slower link and doing this a lot. You own use will quickly determine if this is an issue or not.
I have blathered on, at length, about what I think matters for size and speed here: https://discussions.apple.com/message/17959625#17959625. Some of this may be of use.
I went through a lot of these issues when I tried to fit everything on a 128 GB SSD, so I know some of the issues you are facing. As I noted before, you really only need a Library (minus most Masters) of about 30 GB and that is with large, high quality Previews.
I actually took the SSD out and stuck it in an ancient MacBookPro (in preparation for a trip to Blighty this summer) and have not noticed a huge drop in Aperture speed. (I do miss the speed of applications launch, restart, however.) One thing that I did find that made a small, but nice difference, was keeping all of the Masters on a separate, dedicated drive. Once defragged, etc. that was very fast. Don't know if you could achieve the same results by partitioning a larger drive, but it might well be fun to find out.
DiploStrat