Using Lightroom Via External Drive

Question

My computer's hard-drive is small and would soon get overwhelmed if I stored my master-images there. My plan is to store my master-images on an external drive.
Here is my planned set-up/workflow: I work with previews in Lightroom, back up my LR catalogue regularly as I exit, and only access my master-images when I wish to export/print/copy an image.
Along with this I would keep a regular back-up of those master-images on another drive.
Will this work? Is there anything I've missed here? I'd appreciate some comment keeping in mind the aim is saving hard-drive space on my computer along with ease and convenience of work-flow. If there is a better way of doing it, let me know.

Answer 1

I am going to assume you are working with RAW images and that these originally were stored on your local HDD and that you would prefer to work with these files on an external HDD instead. You have moved the files to the external drive and now you are trying to clean up your local HDD by deleting the old image files after copying them from the local drive to the external drive but you don't seem to be getting back any of the space on your local drive. Is that a decent summation?
Based on that, the post from 99Jon is the correct approach. Copy the local files to an external drive and then tell Lightroom where to find the images by pointing Lightroom to the directory structure on the external drive using the Find Missing Folder option by right-clicking on the top level folder. This will allow Lightroom to rebuild the links between each image in the catalog and the storage location of the image. If a folder in the left hand Folders panel is dimmed however, you still have a disconnect between Lightroom and the physical file.
If the folder is NOT dimmed in the Folders panel that Lightroom does have a link to the physical file and if you tell Lightroom to delete the image, it will be deleted. Kind of. If you select an image and delete it in Lightroom, the default is to delete the image from the catalog only. You have to specifically select the option to remove the image from both the catalog and the HDD. If you go this route, make sure the folder you are referencing is not pointing to your external drive or that is where you will delete the image from. You can check that by first right-clicking on the folder in the Folders panel and selecting Show In Finder.
Lightroom does not like it when you manipulate files using the Finder but sometimes, it is the best way to do what you want to do. Once you have completed the copy from the internal HDD to the external HDD (you can actually do this from within Lightroom), linked the Lightroom catalog to the new folders on the external drive and confirmed you have all your images linked up then the easiest way to remove your images from the internal HDD is to use the Finder to move them to the trash can. You will later have to empty the trash to regain all of the disk space however. This will clean up the space used by your images but there is also the Lightroom catalog and the preview files that will also be taking space.
The catalog does not actually contain any image data. It only contains references to the locations where the original image and the previews are to be found. There two files of interest here. One is the xxx.lrcat file which is your catalog and the other is the xxx.lrdata file. The lrcat file is your actual catalog while the lrdata file contains your previews. If you have generated smart previews, they will be stored in a file named smart previews.lrdata along with the two other files already mentioned. Finally, there is also a folder where Lightroom stores all of your catalog backups called Backups (my backups folder is actually located in a folder called Catalog templates). Every time you close Lightroom, it will create a new copy of your catalog unless you tell it not to. All of these folders are contained in a Lightroom folder in your Pictures directory (again, unless you set things up differently). You can save some space by removing some of the older backups since Lightroom will not clean that up for you. You may also have some old catalogs out there if you have been upgrading from one release to the next. With each new version, Lightroom makes a copy of your current catalog and then updates it for the new version so you may see some from Version-3, Version-4 as well as the Version-5 catalogs. Old catalogs and their associated backups can be deleted.
I have a small working catalog on my Macbook Pro with about 2000 images. My catalog is pretty small (about 20MB) but the previews file is nearly 5GB in size.This is where your 1:1 previews data is stored and Lightroom will manage it for you. You can change your preferences to automatically delete them in a few days, thirty days or never. The default is to delete them after seven days (I think) but, if you open an image for which Lightroom does not have a preview, a new one will be generated using the original image data and then applying all of the changes that have been made to the image which are stored in the catalog. If the original image is offline, a new preview can't be made which can cause a problem if you plan was to be able to update your images offline.
This is where the smart previews come in. This must be generated either during import or by selecting the image/images and then using the Previews/Build Smart Previews menu option. These will be stored in the other lrdata file and are actually smaller size than the 1:1 previews you would normally generate. These need to be maintained always as this is really the only way Lightroom will allow you to make changes in the editor to image files that are offline but, this will require HDD space on your internal drive as will the lrdata file containing the 1:1 previews. The one caution I would offer is not to remove anything from the trash until AFTER you have restarted Lightroom and verified all your images are still intact and none of the folders are dimmed in the Folders panel. Only then will emptying the trash by safe to do.
Not knowing how big your image files are, I can't advise how much space you can get back. My RAW images average about 30MB each. If I shoot using JPEGS, the file sizes are closer to about 9GB each. While I convert my images to DNG files which can save some space over the RAW sizes, I also save my original RAW image in the DNG so I end up with images files that are often 55MB each in size. If I delete ten images I clear more than 0.5GB of space. so it really depends how big the files that you delete are. Also, the savings does not show up until I remove the deleted images from the trash can.
I know this a whole lot of stuff to wade through but there were a lot of questions being asked so I hope this all helps...