Date: Thu, 7 Mar 2002 06:33:50 +0100 From: Cliff Sarginson <csfbsd@raggedclown.net> To: questions@FreeBSD.ORG Subject: Re: Softupdates on root in 4.5-RELEASE Message-ID: <20020307053350.GA2142@raggedclown.net> In-Reply-To: <20020307030446.19E24BA03@i8k.babbleon.org> References: <47615415@toto.iv> <20020306144816.C2BBFBA03@i8k.babbleon.org> <20020306145517.GE4280@raggedclown.net> <20020307030446.19E24BA03@i8k.babbleon.org>
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On Wed, Mar 06, 2002 at 10:04:45PM -0500, Brian T. Schellenberger wrote:
> On Wednesday 06 March 2002 09:55 am, Cliff Sarginson wrote:
> | On Wed, Mar 06, 2002 at 09:48:16AM -0500, Brian T. Schellenberger wrote:
> | > On Wednesday 06 March 2002 09:35 am, Cliff Sarginson wrote:
> | > | On Wed, Mar 06, 2002 at 03:19:26AM -0600, Mike Meyer wrote:
> | > | > I personally make the root partitoin larger, enable soft updates, and
> | > | > use SCSI disks with proper tagged queuing support so the write cache
> | > | > isn't a problem.
> | > |
> | > | Can you clarify this a bit.
> | > | With a SCSI disk, tagged queuing etc, soft-updates are not helpful ?
> | > | yes or no ?
> | >
> | > No. That is, they ARE helpful.
> | >
> | > But with tagged queuing on a SCSI disk, write caching isn't dangerous, so
> | > there's no reason not to use it.
> | >
> | > With an IDE disk, write caching IS dangerous.
> | >
> | > Another advantage of SCSI.
> |
> | Ok, so currently this BSD system runs off SCSI with soft-updates on
> | everything, except root.
> |
> | Would you recommend that optimal performance would be achieved, without
> | danger, by enabling write-caching as well ?
>
> Yes, if you have tagged queuing. Check your messages (dmeg).
>
Mounting root from ufs:/dev/da0s2a
da0 at sym0 bus 0 target 6 lun 0
da0: <QUANTUM ATLAS_V_18_WLS 0230> Fixed Direct Access SCSI-3 device
da0: 80.000MB/s transfers (40.000MHz, offset 31, 16bit), Tagged Queueing
Enabled
> | And what would you recommend therefore with root, which has neither
> | enabled at the moment ?
>
> Provided it's reasonably large (say, over 100M).
>
Yes it is larger than that.
> But you can't enable/disable write-caching on a per-partition basis anyway.
Yes, of course.
>
Ok, that sounds good.
Mmm. I am curious and will try this.
One thing for anybody considering wanting to go broke in a hurry, I
personally can verify that SCSI makes a *huge* difference on a system.
Buildworld, compared to doing it on my IDE drives, just blinks by in
comparison. If this may make it even faster I will be impressed :)
But the price differential is phenomenal ...at least here in Holland :(.
e.g 40GB 7200 ATA 100 = 138 Euros (c. $160)
36.7GB 7200 SCSI U160 = 389 Euros (c. $480)
Also I get the feeling SCSI drives seem to have their sizes specified
where 1K = 1000, IDE drives where 1K = 1024.
--
Regards
Cliff Sarginson -- <csfbsd@raggedclown.net>
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