[gpfsug-discuss] file layout API + file fragmentation

Aaron Knister aaron.s.knister at nasa.gov
Sat Nov 4 16:14:46 GMT 2017


I've got a question about the file layout API and how it reacts in the
case of fragmented files.

I'm using the GPFS_FCNTL_GET_DATABLKDISKIDX structure and have some code
based on tsGetDataBlk.C. I'm basing the block size based off of what's
returned by filemapOut.blockSize but that only seems to return a value >
0 when filemapIn.startOffset is 0.

In a case where a file were to be made up of a significant number of
non-contiguous fragments (which... would be awful in of itself) how
would this be reported by the file layout API? Does the interface
technically just report the disk location information of the first block
of the $blockSize range and assume that it's contiguous?

Thanks!

-Aaron

-- 
Aaron Knister
NASA Center for Climate Simulation (Code 606.2)
Goddard Space Flight Center
(301) 286-2776



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