Camera Raw cache size and location

Question

I've been using ACR for about 3 years now, and today it occurred to me that I'm not that sure I know what the cache is actually used for. I mean, I know what a cache is, but what is ACR caching, and why?
I use Bridge for most of my photo work, displaying high quality thumbnails and previews, often full-screen ("monitor-sized previews" by default). Bridge has its own cache, which I understand contains jpegs of thumbnails, previews, and 100% views. Does ACR's cache have any bearing on Bridge's behaviour and performance, especially with thousands of raw images?
What sort of size and location of ACR cache should I be using - what factors do I need to consider?

Answer 1

Hi,
I'm still not sure what size of cache I should use, and what are the advantages and disadvantages of bigger or smaller ACR caches.
Maybe Eric can tell something indeep about the impact of a large cache.  I'm not sure about that myself, but don't believe a larger cache is a real disadvantage, as long the disk on which it reside is maintained: defrag often). Since Bridge and ACR work hand in hand here, it might depend to your workflow and to your hardware. Sorry, I can't give a clear answer here.
As said I would put it just large enough for a certain number of RAW or some weeks work. Means, when there is a chance I'ld touch a certain RAW in six weeks again, than six weeks * x images per day I shoot.
Not sure if you are a Pro. I'm not and usually have not much new images every month.  I always was fine with the default settings.
I don't work with Bridge and open one RAW after another in ACR, or maybe 20+ in a row when doing panorama ;-)
But Bridge has to do a lot of work on the fly when it generates the previews for all new RAW in a folder, like: "read the image from HDD", "process it by ACR, "write Bridge previews and metadata to HDD", "write to ACR cache " - not necessarily in this order.
And it seems it does this and some additional steps always (not only when first time reading RAW), because it f.e. needs to check if there are already processing information in ACR database or XMP file for a RAW or if they have been created in "meantime". Means ACR settings could have be changed after Bridge did a first time generation of the cache data, maybe because the RAW was openene directly via PS or by another app.
this process is fairly processor-dependent, especially now that ACR uses more sophisticated processing in version 6, and, depending on ACR defaults, this can be significantly slower than in previous versions.
And Bridges eats huge amount of memory as well - seems it holds a lot of information in memory before flushing it to disk.
After reading this post of yours I made a test with my 12k RAW the other day. I tried to let Bridge create previews for all of them in one step, but it ended up complaining that there is not enough memory after ~ half an hour.
Bridge appears to generate previews unnecessarily sometimes, because every image is already cached.
See above. Bridge/ACR checks for updated processing information in XMP or ACR database and metadata updates. If it find some it might need to rebuild its cached image.
Why would I need to reset the cache with a new monitor profile? Surely this is not applied to cache JPEGs?
You are right, sorry I mixed things up here :-(  I meant ACR camera profiles. Aside that I changed monitor profile a lot over the last weeks doing some tests, and after that Bridge often refused to start until the cache was purged…
Your suggestion of a larger cluster size is very interesting, and I may try this when I have some spare time.
All my disks meant for storing large files (images, music, scratch, temp-file) are formated with a larger cluster size. It speeds things up a bit.
Supposedly Lightroom's catalogue system is superior, but I am yet to be convinced that putting all my XMP data in one basket is a good idea.
Of course LR shares ACR's cache. I don't know much about LR, but I believe XMP are not only kept in one basket here, right? They are written to the images and in case of RAW to XMP files. Otherwise there wouldn't be an interoperability between LR and Bridge. Similar to Bridge LR stores previews in it own "cache" which is as well a folder and file based "database". Check "preferences".
But as said I use another DAM, in which’s database all data needed for searching is kept, but I also write all metadata (IPTC,XMP) to the images, even for RAW files. By this I don't need a large ACR cache and also don't have XMP files around, which I hate. When saying database, I mean a real database, not a collection of files which are kept on disk. ;-)
Aside other advantages, I can take my database with me on vacations and can work on my images like I do at home. I have all my keywords and categories with me in one file and when back, I just copy the database to my desktop.