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Thu, 21 Feb 2008

CacheFS and NFS local caching.

David Howells of RedHat recently posted next round of his CacheFS implementation. Main idea of the project is to store locally data and metadata modification on disk.

Cache is implemented as write-through one. Locally data is stored as usual files on a special partition formatted as one or another filesystem.

David also posted benchmarks of his apporach. Metadata intensive operations showed significant slowdown with the local on-disk cache, getting metadata from local cache also shows a slowdown. The former can be explained by the write-through nature of the cache and slow local disk operations, which is also a reason for metadata reading downgrade of the speed.
There is also no cache-coherency algorithm implemented for CacheFS. Another problem, pointed also by Kevin Coffman is possible slower reading of data from the cache than from the local filesystem (and from remote one if bandwith is not a limiting factor which is frequently the case).

This is third (actually the first :) local cache implementation for the network filesystem, so competition between CRFS, POHMELFS and CACHEFS becomes even more interesting :)
Stay tuned!

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