I've a problem with Vaults (thread) that is giving me concerns about the integrity of my library despite Fixing Permissions, Repairing the library, and even Rebuilding the library so I read up about using multiple libraries and exporting/importing between them and, as it is so easy, I exported all my projects as libraries, created a new library, and imported all the exported libraries into it.
It hasn't solved the original problem but I've noticed that the old library is 27.2GB whereas the new one is 16.67GB - nearly 12.5GB smaller!!
OK, so I expect there to be some accumulated dross - this library started life at version 2.2.x so it's been around for a while, but 12.5GB!!!
So, using Show Package Contents I looked for the differences. The two major ones are Previews and Thumbnails - I didn't copy previews when I exported the projects so they have been recreated in the new library.
The differences are:
Previews:
Old library: 8.8GB, 51,440 items
New library: 6.4GB, 49,738 items
Thumbnails:
Old library: 17GB, 63,926 items
New library: 7.4GB, 64,527 items
How can so much dross accumulate in the library?
What's really confusing me is that the number of items (which I assume includes folders as well as files) is roughly the same between the two libraries. Also confusing me is how can the number of items be 3-4 times the number of photos in the libraries (~16,000).
BTW, they are Referenced Libraries.
It could be that the libraries have different settings for image quality for thumbnails and previews. I have a library with 1105 Nikon D800 raw image files in it. This is a 36MP body. I had high quality previews for all 1105 images. The Library was 97GB. I removed all of the previews and it dropped to 53GB. I think Aperture saves several different sizes of the previews, not just one size, so removing the previews can have a very significant impact on the space consumed by the Library.
[ UPDATE ]
As an additional test, my master library of 43045 images consumed 757.36 GB of space. I just deleted all of the previews from the master library. After deleting the previews the space dropped down to 711.14 GB.
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Thanks Walter. I guess it is the multiple previews that are the cause. It just seemed such a massive saving in space. Most of my photos are 10Mpx CR2 files.