[OpenAFS-devel] good and bad performance of memory cache

[Lyle Seaman]

> Note that memcache size and diskcache size are different things.
> In the case of memcache, a fixed number of chunks are allocated
> in memory, such that numChunks * chunkSize = memCacheSize.  In
> the case of disk cache, there are a lot more chunks, because the
> disk cache assumes not every chunk will be filled (the underlying
> filesystem handles disk block allocation for us).  Thus, when you
> have small file segments, they use up an entire chunk worth of
> cache in the memcache case, but only their size worth of cache
> in the diskcache cache.

This is a good point, however in Ed's scenario all his chunks are full -- or 
should be.

The default chunk size is (or used to be) smaller for mem cache, than for disk 
cache, btw.