On Wed, Dec 14, 2011 at 01:40:22PM +0100, Paolo Bonzini wrote: > If the partitions are aligned, the OS will always issue aligned requests, > because file system blocks are already 4k.
It won't nessecarily. For example XFS will do a fair amount of sub-blocksize I/O for metadata and the log. Note that if you tell XFS that the minimal_io_size is 4k it will at least align the log write to it, which is what really matters.
