Lightroom Classic 8: Previews catalog problem

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  • Updated 8 months ago
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I have an Imac Pro 32 gb of memory and a 1tb ssd internal hard drive.  I have a 16tb external thunderbolt hard drive.  I updated to LR9, but was having lots of problems...called support and was escalated to a senior tech.  He reverted me to LR8.4.1.  Running good, but I had to recreate my previews catalog.  So far I have created 1:1 previews of 100,000 of my photos.  the catalog is 1.4tb.  It took 4 days to create these previews.  When it was finished I closed LR to have it do a backup.  The first part went well but it bogged down when it started to optimize the previews catalog.  After 8 hours I called support and was told to be patient as it was a large catalog.  At 24 hours I got intermittent messages that LR was not responding.  At 30 hours I got a message that my system resources were at a critical stage and I needed to exit LR.  I called support this morning  and was told that they would have a senior tech call me this week.  Seriously.  
I can run LR, but am not sure that the 1:1 previews are accurate because I had to interrupt the optimization.  
Does anyone have any suggestions or thoughts on what my next step should be?
Thanks for any help.
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Bill Wood

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Posted 8 months ago

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Johan Elzenga, Champion

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There is no such thing as a ‘previews catalog’. The previews are stored in a folder inside the catalog folder. On Windows this is a normal folder, on Mac it is a so-called package. A package is a folder that looks like a file and can be double clicked in the Finder.

Lightroom can and will rebuild any preview that it needs. There is no reason for you to build thousands of 1:1 previews. Let Lightroom build them if and when it needs them. A 1:1 preview is only needed when you zoom into 1:1 to check things like sharpness and noise. It is not needed for day to day work with your images. Lightroom will keep the previews up to date.
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Cletus Lee

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When LR Classic v9 converted your older catalog file, it renamed your previews folder to " {new catalog name} Previews.lrdata".  just rename that to " {old catalog name} Previews.lrdata". And make sure it is in the same folder as your old 8.4.1 catalog file. 
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Edmund Gall

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One other fundamental question to consider: Why do you need to regenerate 1:1 previews for all 100,000 photos? Correct me if I'm mistaken, but you only really need a 1:1 preview when you're editing photos: so, if you've finished editing them, why keep the 1:1 previews (or regenerate them) and waste all that disk space?..
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Johan Elzenga, Champion

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No, you don't even need them when you are editing, because the Develop module uses its own (different) previews. Like I already said: you only need 1:1 previews if you are checking things like sharpness and noise at 100% view (in the Library module). Generating 100,000 1:1 previews is a waste of time and drive space.