Our ISA server administrator is saying this:
How the ISA cache works is as follows: when the ISA server receives a request to access a website, the first step it takes is check through the cache to see if it can load it locally. As the cache is currently 50Gb in size, the server has to check through this entire cache file before a) directly returning a result to the user or b) passing the request out to the internet to retrieve the web page (and in turn place it in cache). Having to parse this much data is likely to be slowing down the internet access.
Having a smaller cache would be beneficial in that the ISA server can handle requests faster by not having to constantly check the local disk for lengthy (in computer terms) periods of time.
He is advising we reduce our cache file from 50GB to 10GB.
While I agree with his sentiment, surely, this could be taken to extremes: if I don't have any cache file, surely I can skip those horrible slow disks, and just go to the nice fast Internet every time I get a request.
The question therefore: what is the optimal size for an ISA server disk cache file? Does ISA server have a convenient index or hash-table of cached requests such that it doesn't matter how large the cache file is, it will be able to find the offset of any cached content you want, inside that file in O(1) time?