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brettb77712916
brettb77712916
Participant
March 22, 2018
Answered

Lightroom classic - large slow backup - very large preview file

  • March 22, 2018
  • 3 replies
  • 3654 views

I have an updated iMac with PS Lightroom classic cc and and 8TB external drive I keep my photo archive on. Lately the previews file has grown excessively large and is taking almost an hour to backup. The catalog has 200k images, the catalog file is 2.4GB and the preview file is weighing at 550GB! I have the prefs set to standard 2048 pixel preview, HQ preview and discard 1:1 preview after 30 days. Most of this has to be from before 30 days ago. I don't understand why it's not tossing the older ones. How do I get my previews back to a reasonable size? Do I have to dump all them and start over? This could take a long time but I want it to be smaller and realistic to backup often.

This topic has been closed for replies.
Correct answer JohanElzenga

It sounds very reasonable to get rid of the edit history to save on info in the catalog. Is it possible to not have the histories created in the first place? How do I delete one photo edit history or all edit histories? If I understand this would not effect the edits applied in LR but would just remove the history of the order of edits? I first want to confirm all past edits in LR would still be there layered on top of the RAW file, just not the history of the order of edits. I assume it is similar to the history brush list in PS.

I may need to dump some of the 1:1 previews of files I don't view often to save disk space. I'm not positive but It appears it is not dumping 1:1 previews even though I have the pref set to 30days. I assume this because the file is huge. Is it true that every time going in develop a new 1:1 preview is created and it is not using the 1:1 in the preview file? I was hoping the rendered 1:1 previews saved me time getting the highest quality preview in Develop but it sounds like it is not.


The History is just a list of what you did. Deleting it only deletes that list. It does not change the edits and does not change the possibility to change the edits. It's not possible to not have a history created in the first place, but you can safely delete it. To do so select all the photos, go to the Develop module and choose menu 'Develop - Clear History'. You'll get a dialog asking you if you want to clear it for the active photo, or all selected photos.

The Library previews are different previews than the ones used by the Develop module, so a 1:1 preview in the Library is only created when you zoom in while in loupe view. For the same reason it is useless to create 1:1 previews with the intention of doing this for speeding up the Develop module.

3 replies

D
dj_paige
Legend
March 23, 2018

There's no need to make backups of the previews. If they are lost somehow, Lightroom will re-create them.

JohanElzenga
Community Expert
JohanElzengaCommunity Expert
Community Expert
March 23, 2018

dj_paige  wrote

There's no need to make backups of the previews. If they are lost somehow, Lightroom will re-create them.

That's true, but it will take several days to recreate more than 200K previews and in the meantime it will slow down things a lot if previews have to be rebuilt before you can see the images. So if you can spare that backup disk space, it may still be a good idea to backup your previews as well.

-- Johan W. Elzenga
JohanElzenga
Community Expert
JohanElzengaCommunity Expert
Community Expert
March 23, 2018

Just to make sure we're talking about the same thing: are you backing up the previews with a general backup utility and is this taking an hour, or is Lightroom taking an hour when it makes a catalog backup? A catalog backup is just what the name implies: it's a backup of the catalog file only. The size of your previews is irrelevant in this case.

-- Johan W. Elzenga
brettb77712916
brettb77712916Author
Participant
March 23, 2018

Thanks for the info Johan and DJ.

To clarify this is taking a long, long time when backing up from Lightroom when closing. I do make a separate backup of the external drive but that is not the issue. I don't know if this is a factor but I have the catalog stored on the external drive with the images. I could break the catalog into parts but that has other issues. Good point about iLightroom only backing up the catalog and not previews. I tested the three backup options: Backup without optimizing or integrity checked = 3 minutes.  With optimizing no integrity check = 7 minutes. With optimizing and integrity check = 44 minutes. I had this checked thinking it was safer but obviously it is causing the long delay. Why? Is it reading the preview file to check integrity. Am I risking anything not checking integrity on backup? I have definitely noticed a slowing overall in Lightroom and some crashing when I do a bunch of edits. I wish there were a way to purge some of the preview files not viewed recently to drop the size without starting from scratch re building all these previews that may take days. When editing I like to have the 1:1 previews on screen but I don't need all of them. 

    D
    dj_paige
    Legend
    March 23, 2018

    A backup that doesn't have its integrity checked could have problems, ad so its not really a backup at all.

    kglad
    Community Expert
    kgladCommunity Expert
    Community Expert
    March 23, 2018

    [moved from Adobe Creative Cloud to Lightroom Classic CC — The desktop-focused app]

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