J
jpaetzel
Guest
We've been playing more and more with the "force 4K" option in the ZFS volume creation.
It has some caveats: L2ARC devices and hot spares don't have pool meta data on them, so they can get lost if the OS changes their device names.
It seems to provide a performance boost across a wide range of devices, not just those that have native or emulated 4K sectors.
This would be a great place for people to post some iozone stats of their pools with and without the 4K option. We are moving towards making it the default and always using it.
To keep test sizes small, I recommend putting in the following tunable:
hw.physmem 4294967296
Once you've set this tunable you'll need to reboot. Also if you have the autotuner enabled or have any kmem_max, arc_max type tunings you'll need to disable those, either that or change the value of -s to be larger than RAM, but beware, with large test sizes this test can run for a long time.
Then run the following test and post the results here:
It has some caveats: L2ARC devices and hot spares don't have pool meta data on them, so they can get lost if the OS changes their device names.
It seems to provide a performance boost across a wide range of devices, not just those that have native or emulated 4K sectors.
This would be a great place for people to post some iozone stats of their pools with and without the 4K option. We are moving towards making it the default and always using it.
To keep test sizes small, I recommend putting in the following tunable:
hw.physmem 4294967296
Once you've set this tunable you'll need to reboot. Also if you have the autotuner enabled or have any kmem_max, arc_max type tunings you'll need to disable those, either that or change the value of -s to be larger than RAM, but beware, with large test sizes this test can run for a long time.
Then run the following test and post the results here:
Code:
iozone -r 4k -r 8k -r 16k -r 32k -r 64k -r 128k -s 6g -i 0 -i 1 -i 2