> When sequential I/O is done to the disk directly there is no performance > degradation at all.
All filesystems impose some overhead compared to the rate of raw disk I/O. It's going to be hard to store data on a disk unless some kind of filesystem is used. All the tests that Eric and I have performed show regressions for multiple sequential I/O streams. If you have data that shows otherwise, please feel free to share. > [I]t does not take any additional time in ldi_strategy(), > bdev_strategy(), mv_rw_dma_start(). In some instance it actually > takes less time. The only thing that sometimes takes additional time > is waiting for the disk I/O. Let's be precise about what was actually observed. Eric and I saw increased service times for the I/O on devices with NCQ enabled when running multiple sequential I/O streams. Everything that we observed indicated that it actually took the disk longer to service requests when many sequential I/Os were queued. -j _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
