Curious if anyone has gone down the route of creating a fuse filesystem
implementation around Memcache, kind of along the lines of CacheFS.
The problem with CacheFS, is your limited to the amount of memory on the
given machine and the usual problems of cache consistency. MemcacheFS
would extend this principle to work on exported/distributed filesystems
and benefit from the distributed/fault tolerant design of Memcache.
Essentially, it would act as a layer between a networked file system,
storing small objects on demand (cache miss) and stat caches in in
memory. Readdir() operations would fall back to disk.
Our specific application deals with millions of small xml files, 5-10k
each. We don't care about readdir operations very much. Often the files
are accessed directly from within an xslt processor that is not memcache
aware, not to mention numerous other applications which cannot be easily
modified to utilize Memcache natively. Further more, scaling Memcache is
a lot easier than scaling many distributed filesystems; it's just to
fire up another process and add it to the pool. Memcache has been
ideally suited for enhancing the performance of database driven
applications, why not apply it to another kind of database -- the
filesystem?
I am curious what everyones' take is on this idea. Does this sound like
a practical solution? What would be your critique against it or other
concerns, permissions and security aside. Keep in mind, the underling
filesystem is already network based, thus this would not significantly
increase network IO. Clearly, I'm tailoring this to our specific needs
of accessing small files. The solution would be dramatically more
complex for storing large files and would probably require striping of
some sort.
Best,
Erik Osterman
