Happy Tuesday everyone! I got a couple of comments concerning yesterdays Lightroom video on having your images on an external folder vs having a catalog on an external folder. I figured it’s a good a time as any to talk about what the difference betweens catalog, data, and images in Adobe Lightroom, and why I set myself up the way I do.
(Click here to get a trial of Lightroom 2 – you know you want to 
)
The Lightroom lrcat and lrdata Files
(agreed that this may be an oversimplification of the process here.. but it’s enough for you to understand what Im doing… )
When you work with Lightroom, the program works like a giant hall monitor – keeping track of where your images are located (on a hard drive, on an external drive, what the folder structure is) as well as keeping track of any changes that you make to them such as keywording, ranking, flagging, collections and -processing-.
To do these two things, Lightroom creates a couple of files – the lrCat file and the lrData file. The lrcat file is the file that holds all of this and is a type of a database that keeps all of these records in order. The lrdata file for the most part holds the previews of the images – but not the original images. In that, the lrcat file remembers the “location” of where you put the file.
Why all of this Rocks
Now, this is really what I think makes Lightroom ROCK in terms of use, and why everyone needs to use it. When you are working with images in Lightroom, you’ll notice that your processing of them is FAST. Making exposure changes, adjustments, changes in tone – all of it runs very very quickly, and completely editable. You can go back SO MANY steps in the process because all of this information ISNT being saved to the file itself. All of these changes that you’re doing (Even brush based /crop adjustments in the develop module) are a type of metadata thats being stored in the catalog. All of these changes arent applied to the image until you export out or edit to in Photoshop, which I think is sweet!
My Recommendation
Because the lrcat and the lrdata files are files that are in constant use from Lightroom, it is why I always keep those files locally on the hard drive. The images are the only thing that I remove from the computer and store on an external drive – and sometimes even move them around in drives. That part doesn’t really matter.
If by some chance I move the file to a new hard drive, and Lightroom cant find it, Lightroom will say “Hey.. I cant find this file.. tell me where it is.” You then have an option to go and point to where you moved the file to. Lightroom is additionally smart in that it will then go and make sure that all of the other references to those files are updated in Lightroom (specifically the lrcat file).
Without those two files, Lightroom wont start, so its essential it can always find them.. the images.. not all that important – comparatively speaking.
Backup, man, Backup!
This also brings up the point of backup. You can set Lightroom to backup at specific points.. and what it does is take copies of your lrcat and lrdata file and store them for safekeeping. The problem here is that if you have a large database.. these things can get pretty big. I my example above, 2 days of backups equal almost 1/2GB. That can get big pretty fast..
As a strategy, I say backup as often as you need to in your case.. but after a few backups (Lets say 5) delete all of the other ones. You wont need them. If you’re incredibly paranoid, you can take one of them and place them in an external drive.
(Click here to get a trial of Lightroom 2 – you know you want to )
This should give you a good idea on how to use Lightroom 2 on a machine and not have your shoots take over all of your space. Obviously if you have any questions, feel free to comment or ping me on Twitter! See you guys back here tomorrow!
Not sure about Macs, but on Windows the .lrdata folder (which holds the previews) gets huge and unwieldy and there doesn’t seem much point in backing it up. In fact I now occasionally delete the whole folder because LR will create a clean version again automatically.
You will lose your previews of course but LR creates them again for whatever folder you looking at in the Library module.
You wouldn’t want to do this whilst in the middle of a close examination of your recent imports but as a housekeeping measure you’ll save a heap of wasted space by occasionally deleting the .lrdata folder – NOT the .lrcat file – which is, or will become the most important file on your computer for the reasons given above!
New to LR and puzzled by the following: I store my photos on external HD: Top folder “LR pix”, and subfolders by date. Twice, don’t know why/if my fault, I’ve been told it can’t find the top folder. So I point it to it, but it can’t then find the subfolders in one step, wants me to do each and every one of the several hundred. It was easier to restore from backup than do that. Any idea as to what’s up, and is there an easier way to restore the connections?
Thanks!
RC, thanks a million for blogging on this issue…it’s great timing for me. Last week I received my Western Digital My Book studio edition 1TB external drive, firewire 800. I’ll probably set it up this weekend, maybe next.
It was a good deal at B&H, $170… Thanks again, and keep the good stuff coming!
Is there a way to back up before I quit the program. I don’t like waiting until I open Lightroom up the following day. I recently lost some editing with a corrupted catalog that could not be fixed.
Great tips. Was wondering whether keeping the lrcat and lrdata files on the secondary hdd within my Mac makes a difference in performance, rather than on my main OS drive.
This is off topic, but I also would like to know whether you can select the images in a stack with one click instead of opening the stack and shift clicking the first and last image.
Note that the lrcat is just a sqlite file/database and can be accessed from any sqlite library, which is really handy for stuff like tagging from outside of lightroom and automating stuff in the programming language of your choice. This is what I like most about LR (btw Aparture does the same).
Edit – 3rd paragraph from bottom – “I my example above, 2 days of backups”…”I” should be “In”