Path: utzoo!attcan!uunet!mcvax!philmds!prle!cstw01!meulenbr
From: meulenbr@cstw01.UUCP (Frans Meulenbroeks)
Newsgroups: comp.sys.atari.st
Subject: my ideal cache program
Message-ID: <157@cstw01.UUCP>
Date: 30 Jun 88 08:04:11 GMT
Reply-To: meulenbr@cst.UUCP ()
Organization: Centre for Software Technology, Philips Eindhoven
Lines: 38

After seeing a number of cache programs, I decided to scribble down what
I wanted to see in an ideal cache program.

I am posting this for two reasons:
1) to get feedback about missing items, problems to be expected etc.
2) because I have little time to start the actual implementation, someone
   else might give it a try. (Hint, hint). If you want to, drop me a note
   saying so, in order to avoid duplication of effort.
   Don't expect an implementation from me soon.

How my ideal cache looks:
- startable from auto folder or accessory which installs itself silently
- settings (like size) taken from program name or data file
- resizable when in operation
- selectable which devices are cached
  (it is not too useful to cache a ram disk)
- works both with floppies and hard disks
- selectable whether or not write-through
- if not write-through:
  - has an auto "sync" facility, which will flush all written buffers
  - interval of above facility is user definable
  - has a command to flush explicitly
  - detect media change and warn (insist?!) that the previous floppy is
    re-inserted when unwritten buffers exist.
- intelligent replacement algorithm (something like Least Recently Used)
- (optionally) read ahead (cache the complete track when a sector is
  requested)
- perhaps (optionally) always cache FAT and root dir.

I think this can lead to a safe write-delayed cache.
Since a number of things can be modified during operation, the cache will
most likely be implemented as an accessory.

-- 
Frans Meulenbroeks
	Centre for Software Technology
	...!mcvax!philmds!prle!cst!meulenbr   or   ...!uunet!prlb2!cst!meulenbr
        or perhaps   meulenbr@cst.prl.philips.nl