Can IIS serve Most Frequently Used static files from RAM?

Question

Can I set up an IIS server so that it will cache the most frequently used static files (binary) from disk into RAM, and serve from RAM on request?

Update: mod_mem_cache in Apache Caching Guide seems to be what I'm looking for. Any equivalent thing in IIS?

Thanks.

Answer 1

You may be able to setup a ram drive, and then move your files there and setup IIS virtual directory there.

Answer 2

Set up a RAM Disk if you have lots of RAM

http://www.tweakxp.com/article37232.aspx links to a free one. Have your application copy the relevant files to that drive and set your wwwroot to point at that location.

This data is not safe between boots though.

Also I run a big IIS site and serve tons of static files. The windows file cache is fine and I get more problems on network latency. Time to first byte e.t.c. My disks are never bound. But ram disk will help if you have a known problem.

Answer 3

What Nate Bross said is probably the most reliable way to keep them in ram, assuming the RAM disk is dynamically created from a real disk somewhere at boot.

Additionally, you could set up an asp.net handler (*.ashx) for the files to use the cache built into ASP.Net. It would try to serve from the cache first and only load them if needed. This has the advantage of allowing you to easily expire the cache from the time to time if the file might occasionally change and allow IIS to re-claim that memory if it decides it needs it more for something else at the moment.

Answer 4

In ASP.NET:

Response.Cache.SetExpires(DateTime.Now.AddDays(1));
Response.Cache.SetCacheability(HttpCacheability.Public);
Response.Cache.SetValidUntilExpires(true);

This is to say, not that an ASP Solution is the best, but rather that IIS obeys the caching directives, an may opt to cache in RAM.

However, I believe you can signal IIS to cache a single file in the IIS management snap-in, if ASP/ASP.NET is not an option, by setting the content expiration 1 or more days in the future.

Answer 5

IIS should be doing this already. In .Net this is what the output caching would do for you.

Answer 6

Here's a bit on IIS 6.0's file cache: http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/a0483502-c6da-486a-917a-586c463b7ed6.mspx?mfr=true. As David mentioned, IIS is likely doing this for you already.

IIS 7.0 Output Caching

IIS 6.0 file cache behavior is included in IIS 7.0 output caching. You can define your own rules if the default timeout seems too short. Kernel Caching takes advantage of OS caching.

Answer 7

Even if IIS isn't actually set up to perform caching on its own, for true static files that are only loaded from disk and sent over the wire (i.e. images, .css, .js), you'll likely end up using the in-memory file cache built into Windows itself. In Task Manager, you'll notice a "System Cache" metric in the Physical Memory section; that shows you how much space the OS is using for the cache. So, as long as you're talking true static files, adding explicit caching is unnecessary.

Edit:
For more details, here's a couple links about the Windows cache (you probably could find more with Google):

• http://msdn.microsoft.com/en-us/library/aa364218(VS.85).aspx
• http://support.microsoft.com/kb/895932