Performance bottlenecks

Too much data copying
Data that comes in from a server is ..
Copied once when storeAppend() is called (into the membuf)
Copied again when storeClientCopy() requests it (into the given buffer)
Copied again when storeWrite() is called (the FS code!)

Data needs to be refcounted
This can now be done with the new cbdata allocator, as cbdata operations are now very cheap