Date: Sun, 1 Sep 2002 23:36:39 +0100 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: Peter Leftwich <Hostmaster@Video2Video.Com> Cc: "Greg 'groggy' Lehey" <grog@FreeBSD.ORG>, Giorgos Keramidas <keramida@FreeBSD.ORG>, FreeBSD LIST <FreeBSD-Questions@FreeBSD.ORG> Subject: Re: dd if=/dev/zero of=/dev/ad1 Message-ID: <20020901223639.GA12421@happy-idiot-talk.infracaninophi> In-Reply-To: <20020901152742.M37627-100000@earl-grey.cloud9.net> References: <20020826013322.GD88156@wantadilla.lemis.com> <20020901152742.M37627-100000@earl-grey.cloud9.net>
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On Sun, Sep 01, 2002 at 03:29:20PM -0400, Peter Leftwich wrote:
> On Mon, 26 Aug 2002, Greg 'groggy' Lehey wrote:
> > > True. You might want to use a large block size to speed operations if
> > > possible (less I/O calls from dd(1) to the kernel, and more freedom to
> > > the kernel drivers to arrange in which order data is zeroed). Try at
> > > least 32 KB.
> > The optimum is the maximum transfer size, currently 128 kB.
> > Greg {See complete headers for address and phone numbers}
>
> What determines that the optimum/maximum transfer size is currently 128 kB?
> My HDD and hardware or the most current version of the OS FreeBSD 4.6.2?
It's part of the IDE specification: 128k is the maximum IO transfer
size. Oh --- the equivalent figure for SCSI discs is 64kB.
http://www.freebsd.org/cgi/getmsg.cgi?fetch=2144092+2148744+/usr/local/www/db/text/2002/freebsd-questions/20020811.freebsd-questions
Cheers,
Matthew
--
Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks
Savill Way
Marlow
Tel: +44 1628 476614 Bucks., SL7 1TH UK
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