README

pCacheFS - http://code.google.com/p/pcachefs/downloads/list

Copyright 2012 Jonny Tyers
pCacheFS is license under Apache License 2.0 - see the LICENSE file for details.


pCacheFS provides a simple caching layer for other filesystems. The cache, however, does not disappear when you start/stop pCacheFS or reboot - it is persistent.

It is designed for caching large amounts of data on remote filesystems that don't change very much, such as movie/music libraries.

Key features
* you can choose where to store your persistent cache - local harddisk, ramdisk filesystem, etc
* cache contents of any other filesystem, whether local or remote (even other FUSE filesystems such as sshfs)
* pCacheFS caches data as it is read, and only the bits that are read

Currently pCacheFS mounts are read-only - writes are not supported.

Example
Suppose I have a slow network filesystem mounted at /remote.

  $ ls /remote
  hugefile1 hugefile2 dir3

If I want to use another local directory as a persistent cache for this filesystem, I can use a pCacheFS mount:

  $ pcachefs.py -c /cache -t /remote /remote-cached

I will now have a mirror of /remote at /remote-cached.

  $ ls /remote-cached
  hugefile1 hugefile2 dir3

This is our caching filesystem. We can read files from this filesystem and their contents will be cached in files in /cache. (As well as file contents, metadata and directory listings are also cached.)

So, the first time I access hugefile1 it will be as slow as it would have been via /remote:

  $ cat /remote-cached/hugefile1

But, access hugefile1 again and you'll notice a big speed improvement. This is because the data isn't actually being read from the slow filesystem at /remote, it is being read from /cache.

Note that in order to get the benefit of the cache you must access files via your pCacheFS mountpoint (/remote-cached above, but this can be anything you like). Accessing the target filesystem directly (via /remote above) will not see any speed gains as you are bypassing pCacheFS.