On Wed, Dec 2, 2015 at 8:18 PM, Phil Turmel <philip@xxxxxxxxxx> wrote: > On 12/02/2015 07:12 PM, Dallas Clement wrote: >> All measurements computed from bandwidth averages taken on 12 disk >> array with XFS filesytem using fio with direct=1, sync=1, >> invalidate=1. > > Why do you need direct=1 and sync=1 ? Have you checked an strace from > the app you are trying to model that shows it uses these? > >> Seems incredulous!? > > Not with those options. Particularly sync=1. That causes an inode > stats update and a hardware queue flush after every write operation. > Support for that on various devices has changed over time. > > I suspect if you do a bisect on the kernel to pinpoint the change(s) > that is doing this, you'll find a patch that closes a device-specific or > filesystem sync bug or something that enables deep queues for a device. > > Modern software that needs file integrity guarantees make sparse use of > fdatasync and/or fsync and avoid sync entirely. You'll have a more > believable test if you use fsync_on_close=1 or end_fsync=1. > > Phil Hi Phil. Hmm that makes sense that something may have changed wrt to syncing. Basically what I am trying to do with my fio testing is avoid any asynchronous or caching behavior. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
