Investigating a bit more a device reset will also trigger the
change so after changing the value you can use camcontrol reset
to trigger the change to apply using e.g.
camcontrol reset 0:0:0
THIS actually work.
And the results are disastrous. in spite of NCQ working and fully filled,
when unpacking source tree (as a test) onto UFS filesystem gstat shows at
most 100 IOPS, and average 700 with write cache disabled.
this is on / partition that spans 1/10 of disk. Drive can actually manage
multiple writes in short distance well with write cache enabled.
While this is stated in the man for ada its not obvious that
changing the sysctl without a reset won't work, so you might
want to raise a PR about it.
Regards
Steve
----- Original Message ----- From: "Steven Hartland"
Looking at the cam ata code I can't see how those values would do
anything after booting.
I suspect they should be loader only tunables with the current code
and cant be changed on the fly for a disk that's already been
registered.
Try setting the values in /boot/loader.conf if you haven't already?
You can check the actual status of the disk itself using:-
camcontrol identify ada0
Regards
Steve
----- Original Message ----- From: "Wojciech Puchar"
after reading quite recent topics about disabling/enabling write cache, i
tried to test in on desktop 3.5" drive
kern.cam.ada.write_cache: 1
kern.cam.ada.read_ahead: 1
kern.cam.ada.0.read_ahead: -1
kern.cam.ada.0.write_cache: -1
i tried writing 1 or 0 to kern.cam.ada.0.write_cache, and there were
exactly no differences at all, and disk seems to do always write caching.
Does that drive lie and ignore commands or i do it wrong?
this is my disk.
ada0 at ahcich0 bus 0 scbus0 target 0 lun 0
ada0: <SAMSUNG HD501LJ CR100-10> ATA-8 SATA 2.x device
ada0: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
ada0: Command Queueing enabled
ada0: 476940MB (976773168 512 byte sectors: 16H 63S/T 16383C)
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