[Pvfs2-developers] null-aio

[Phil Carns]

There is a new trove method available in trunk now called "null-aio". 
It can be selected by putting "TroveMethod null-aio" in the 
<StorageHints> section of the file system configuration file.

This is only useful for debugging purposes, because it deliberately 
skips doing any file I/O on the server side.  Please use with caution! 
It does all metadata operations the same as any other method, but file 
reads will return garbage and file writes are thrown away.  Writing 
beyond eof triggers a truncate to mimic the appropriate resulting 
bstream size.

This might be useful once in a while for narrowing down performance 
problems between network and storage.  It takes the storage out of the 
loop and shows approximately what the network is capable of by itself. 
Of course it will only work for benchmarks that don't verify data 
correctness (or otherwise rely on data read off of PVFS).

We used to have a compile time option (--disable-disk-io) for this same 
purpose, but that actually hasn't worked in a while.  Nowadays its 
easier to just do this as a trove method that can be selected at runtime 
without recompiling.

-Phil