LIGHTROOM: Large or smaller preview cache?

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Will a large preview database reduce the performance of LR? I have read the Adobe document about LR performance, and one place it says that the cache should not be too big because of performance issues, and another place in the doc is says that it's only a hard drive size concern.
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kurka666

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  • faster then the speed of Lightroom

Posted 5 years ago

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Rob Cole

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Note: you don't get to set the size for preview "cache" (and previews exist for all files - used primarily in library module). You *do* however get to set the size for ACR cache (entries only exist for raw files, and not DNG w/embedded fast-load data. - only used in develop module). Begs the question: which are you talking about?

You can set the expiration criteria for 1:1 previews, and size/quality of "standard" previews.

My experience? ACR cache is a don't care - set it big, or set it small: won't matter enough to talk about (cache entry sizes in Lr4 are about an order of magnitude smaller than previous Lr versions).

Previews? again, makes so little difference compared to other factors that it's a wonder (to me) that Adobe even exposed options to the users. What I do is set 1:1 to never expire and set quality to maximum, so I can (export or) recover high-quality previews in case disaster strikes. But my performance tests have revealed very little performance difference regardless of settings (note: preview size makes no difference whatsoever if you have 1:1 previews built, it only matters if you don't, in which case it's better to have a "big enough" preview for current demand, otherwise a big enough version will have to be rendered, which is when you see: "Loading...". PS - if you discard all previews, and rebuild standard previews, and you don't see such "loading" when viewing in loupe mode (at fit view, and fill view if you use that), then your standard previews are big enough).

Maybe somebody else has the ability to offer more quantitive info, or has more refined sense of settings differences...

It's worth noting however that most of what you hear about performance as related to ACR cache size is "theoretical" and not realized in practice.

Cheers,
Rob
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kurka666

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Thanks Rob. About the size, I did mean whether to delete the previews after 30 days or not. Currently I use 1:1 previews that never expire too, and by cache is on 60gb. I could of course discard old previews and compare :)

Thanks for your tip about preview size.

I guess it's optimal to keep catalog, images and previews on different disks if possible.
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Rob Cole

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You bet. Bottom line: having 1:1 previews around won't affect performance.

Probably it would be optimal to move previews to separate physical drive from catalog and images, but I've never tried that (you need to set up links, since Lr does not support such separation otherwise).

PS - There is a very slight performance improvement by separating images from catalog - not as big as you might expect. Why not? - because images are accessed in one lump (while catalog is not being accessed so much), and catalog is being accessed all the time, when images (image files I mean) aren't being. Still, worth doing if you've got the drives...

Cheers,
Rob
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kurka666

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Thanks Rob. So this (from http://helpx.adobe.com/lightroom/kb/o...) is probably not correct "Keeping standard previews small also helps reduce the size of the preview file cache, which speeds performance and saves on hard disk space"

I started looking into this now that I bought a sata 3 card for my MacPro from 2009. I had the previews (via a symlink which I hope does not affect the performance) on the HDD which I believed was the fastest, but I found that it is a very slow hdd, so I'll move it to another drive. I'd prefer to store previews on my SSD, but then I have to reduce the size of it. Either by deleting after 30 days or reducing the size of the standard previews.

I'll also consider making a FusionDrive and let the OS determine what is stored where. That is of course the simplest, but it is not necessarily optimal.
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Rob Cole

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In theory, Lr should be able to generate smaller standard previews faster. How much, if any improvement you may experience, in practice, is another matter. Last time I checked it (a long time ago), 1680 was slower than 2048, but 1440 was slightly faster. YMMV - I assumed there was some bug, but it never got acknowleged by Adobe - a few other users were able to bear witness. My advice? test it. And then, let us know what you find.

To test - go into develop module and auto-sync a change (that will make lib previews stale), then return to the library module and measure how long it takes for the loading indicator to be extinguished when stepping from photo to photo in loupe view. Try same experiment with each standard-preview size and see. Consider checking file-sizes in preview folder (.lrdata) too. Maybe use a test catalog and delete all previews (by deleting .lrdata folder, after exiting Lightroom) between tests to avoid confusion.