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Enhancing LFU algorithm

Posted: Sun Aug 28, 2011 12:24 am
by Nina
Hi,

Currently I am using LRU algorithm instead of LFU since it's doing better on my PC & its operating patterns. Anyway, I am wondering if you guys could enhance LFU algorithm a little bit through decreasing 'cache insertion' since there is a file system cache already doing it's job all the time side-by-side with FC, and as you know Windows usually reads most of the data on the storage devices just one time during a session, so isn't it a good idea to add 'ignore cache for a first-time request' ? for example multimedia files are big and usually we don't play the same media files more than once a session. (i.e. all the hot data in FC cache would be evicted if you play a 7GB movie on your HD.. 'cache pollution', think of defragmentation software, AV, etc..) ... and thanks!

Re: Enhancing LFU algorithm

Posted: Tue Aug 30, 2011 9:22 am
by Support
Hi Nina,

Thanks for your suggestion. We'll consider this scenario.

Re: Enhancing LFU algorithm

Posted: Mon Sep 19, 2011 2:26 pm
by Axel Mertes
Hi Nina,

that would require Fancy cache to buffer all read operation block numbers to be aware if it was already read once and ignored.
If you don't do that, each time will be the first time, as you alway ignore it.

I think it could have some signficant speedup for the entire system, but may take some serious more RAM for keeping all required info stored. You need to know that we sometimes have 30+ TByte on a single machine...

At some point we may even consider having a cache block filter based on directory structures or file extension pattern filters. So you may process a MFT regarding these filters in mind, then apply a yes/no caching flag per block and you are done. But holding a large MFT can take some serious amount of space - questionable in a 30+ TByte range IMHO.

Axel