Date: Tue, 18 Sep 2001 19:30:57 -0500 From: Mike Meyer <mwm@mired.org> To: Francesco Casadei <fcasadei@inwind.it> Cc: freebsd-questions mailing list <freebsd-questions@freebsd.org> Subject: Re: soft updates Message-ID: <15271.59201.121267.580652@guru.mired.org> In-Reply-To: <20010918151219.A1300@goku.kasby> References: <89370727@toto.iv> <15270.56819.636304.261065@guru.mired.org> <20010918151219.A1300@goku.kasby>
next in thread | previous in thread | raw e-mail | index | archive | help
Francesco Casadei <fcasadei@inwind.it> types:
> On Tue, Sep 18, 2001 at 12:38:59AM -0500, Mike Meyer wrote:
> > Brian T.Schellenberger <bts@babbleon.org> types:
> > > On Sunday 16 September 2001 20:53, Nathan Mace wrote:
> > > > basically what i'm asking is is it stable? and how much of a performance
> > > > gain am i gonna see? thanks
> > > "Yes," and "a lot", respectively, but you *must* turn off write-cache on your
> > > disk if you are going to use soft updates.
> > Only for IDE drives. SCSI provides features that let you use
> > write-cache safely - if the driver you are using supports the
> > feature. Check the driver manual page for "tagged queuing". If the
> > driver supports that, you can turn write caching on for the SCSI
> > drives attached to it.
> > IDE disks that support tagged queuing are coming and the ATA driver
> > supports them, but the most recent report I have says they aren't very
> > reliable.
> From ata(4) manpage:
Though I expect everyone knows this, the ata driver only supports IDE
drives. SCSI controllers use different drivers - ahc for example.
> [...]
> hw.ata.wc
> set to 1 to enable Write Caching, 0 to disable (default is enabled)
> (WARNING might cause data loss on power failures)
>
> hw.ata.tags
> set to 1 to enable Tagged Queuing support (default is disabled) (only IBM
> DPTA and DTLA drives support that)
> [...]
>
> IBM IC35L0[246]0AVER07 drives support Tagged Queuing and Write Caching. Does
> this mean that I can safely set hw.ata.wc=1 and hw.ata.tags=1 with softupdates
> enabled without going into consistency troubles?
Correct.
> What "recent report" are you referring to? Do you know of reliablity issues
> with IBM drives with WC and TQ enabled?
From the tuning(7) man page:
There is a new experimental feature for IDE hard drives called
hw.ata.tags (you also set this in the bootloader) which allows write
caching to be safely turned on. This brings SCSI tagging features to IDE
drives. As of this writing only IBM DPTA and DTLA drives support the
feature. Warning! These drives apparently have quality control problems
and I do not recommend purchasing them at this time.
<mike
--
Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/
Q: How do you make the gods laugh? A: Tell them your plans.
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?15271.59201.121267.580652>