vinum, 5.x performance, ... (was: Re: ANNOUNCE: GNOME 2.12.1
has been merged into the ports tree)
Alexander at Leidinger.net
Tue Nov 8 01:16:32 PST 2005
Ion-Mihai Tetcu <itetcu at people.tecnik93.com> wrote:
> On Mon, 07 Nov 2005 14:56:45 +0100
> Alexander Leidinger <Alexander at Leidinger.net> wrote:
>> Ion-Mihai Tetcu <itetcu at people.tecnik93.com> wrote:
>> > On Mon, 07 Nov 2005 11:18:00 +0100
>> > Alexander Leidinger <Alexander at Leidinger.net> wrote:
>> >> > - and performaces is a nightmare on atapi harddisks
>> >> AFAIR 4.x enables the write cache (bad if there's a power failure
>> >> in the soft-updates case, since without native command queueing the
>> >> drivers may reorder writes witout the possibility to notify
>> >> soft-updates about it),
I' a little bit confused now. The man page says the WC is enabled by default,
but I was under the impression, that it is disabled by default (I remember
there was a discussion about this long ago). On my systems it is disabled,
since I haven't removed the loader.conf line since the 4.x days. Søren, is
this a bug in the man page or did I got it wrong?
>> > So on NCQ disks write_caching should be safe from consistency
>> > point-of-view ?
>> AFAIK: Enabling the write cache doesn't mean you use NCQ. So just
>> because your drive is able to do NCQ, you shouldn't enable the write
>> cache. If your controller, your disk and the OS is able to use NCQ,
>> and you enable the use of NCQ, then everything is fine... assuming
>> the drive doesn't lie to you. AFAIR there are or there where some
>> drives which lie(d), but I don't remember the details.
> And finding out the what disk and controller use NCQ _and_ are
> supported by our drivers can be done how ?
Asking sos at FreeBSD.org (CCed) would be a way to find it out...
At first I thought atacontrol tells you about it. But the "atacontrol cap
ad0" command just tells you about the capabilities of the drive, not which
of those capabilities are used by the driver (would be nice to have,
specially in the light of seeing TCQ enabled but knowing that you said is
doesn't work... at least with the previous implementation of ata).
Søren, is there a way to en-/disable some of the capabilities with atacontrol
or something else?
http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID = 72077137
The debate rages on: Is PL/I Bachtrian or Dromedary?
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