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Roger Burton
Media cache testing
on Aug 24, 2012 at 7:53:06 am

Hi chaps, so in an attempt to improve performance I followed lots of advice and decided on getting a fast (ish) external drive for my disk cache, thinking that as a 'light' After Effects user it was a good 'bang for buck' way of improving my workflow by improving ram previews.

For better or worse I decided on a 1tb Lacie Little Big Disk (Thunderbolt) on my i5 16gb ram iMac.

So to do a simple test I tried ram previewing a project (having purged all memory) and setting the prefs for cache to a folder on my desktop and timed the preview - then I purged again and changed the folder to one on my new external drive allocating 600gb and, in all honesty, there's little or no difference.

Is my 'testing method' flawed or am I expecting too much or maybe I've not changed the prefs correctly ... or maybe I've just made an expensive mistake !

Thanks for any advice.

Roger


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Roger Burton
Re: Media cache testing
on Aug 24, 2012 at 2:35:47 pm

looking into it further maybe I missed what the external drive was going to help with - performance and persistent disc cache ... maybe that's where the performance/workflow improvements will become obvious, when I'm actually working on a project ?

Roger


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keith mcgregor
Re: Media cache testing
on Aug 24, 2012 at 9:55:29 pm

RAM previews are based on how much ram is on your system. The disk cache should be for, well they explain it better:
"Disk cache
After Effects can store rendered items to your hard disk when the RAM cache is full during standard previews. Blue bars in the time ruler of the Timeline, Layer and Footage panels mark frames that are cached to disk. Note:
The disk cache is not used for RAM previews. It is only used for standard previews."

as found here:

http://helpx.adobe.com/after-effects/using/memory-storage.html

and read it ALL, but what you're looking for is 3/4 the way down the page. Hope this helps!
-Keith


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Walter Soyka
Re: Media cache testing
on Aug 25, 2012 at 1:03:15 am

[Roger Burton] "looking into it further maybe I missed what the external drive was going to help with - performance and persistent disc cache ... maybe that's where the performance/workflow improvements will become obvious, when I'm actually working on a project ?"

Right.

Your initial RAM previews will not be made any faster by the persistent disk cache; however, once a preview is cached to disk, you will not have to re-render it. If you make a tweak, and then undo, you will not have to re-render. If you have multiple layers in a complex comp, and you change one layer, you will not have to re-render every individual layer plus the composite -- just the changed layer and the the composite (the other layers can be pulled from the cache).

If you re-use cached layers or even whole comps in other projects, AE will use the cache instead of re-rendering.

The persistent disk cache does not show well in light demos because some operations are simply faster to render than they are to read back from the cache, so AE won't bother. However, with more complicated or slow-rendering comps, the cache really shows its value.

Todd Kopriva of Adobe has released a great video [link] showing the global performance cache and the persistent disk cache in action.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
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Roger Burton
Re: Media cache testing
on Aug 25, 2012 at 7:55:29 am

Thanks Keith and Walter, as ever, great advice and thanks for the links, I had watched and read those before so please don't think I just post without doing some research but I hadn't really got my head around the principal ... so providing I make my external drive the 'cache' and allocate enough space on that drive all will work (ie I don't have to press any other buttons)? ... Good of you Roger


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