Jens Axboe <jaxboe@xxxxxxxxxxxx> writes: >>> I wonder how many times I saw someone - including myself - fire up >>> bonnie++ or iozone with a rather small test file compared to the full >>> disk size ... Thanks very much everyone! This was an (overdue) eye >>> opener. >> In addition, testing with a file is dependent on the state of the file >> system. For example, if you're using a 100GB file and there's not enough >> contiguous free space to lay it out in one chunk you could have regions on >> different parts of the disk. Further, even there is enough space, that space >> could be near the inner or outer diameter which would also affect >> performance. >> >> There is a way to get a file address to lba map (which would give you some >> insight into how a file is laid out). I think there's a syscall. Jens should >> know. > > Yep, you can use FIBMAP/FIEMAP to walk the extents of the file and get a > full map of how it's laid out on disk. Not sure if there are tools > that'll do this for you, if not is pretty trivial to write. man 8 filefrag; it's part of e2fsprogs. I'm sure xfs has its own utility to do this, too. Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
