From owner-freebsd-questions  Wed Mar 20 12:12:37 2002
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Date: Wed, 20 Mar 2002 12:12:27 -0800 (PST)
From: Matthew Dillon <dillon@apollo.backplane.com>
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To: Paul Mather <paul@gromit.dlib.vt.edu>
Cc: David Greenman <dg@root.com>,
	"Steve O'Hara-Smith" <steve@sohara.org>, mrcpu@internetcds.com,
	clash@tasam.com, questions@FreeBSD.ORG, stable@FreeBSD.ORG
Subject: Re: Problems with large disk. (> 1 TB)
References: <20020319131556.D99985@backmaster.cdsnet.net> <008901c1cf8c$be5d6f50$090510ac@gleason> <00b401c1cf8d$8960b7c0$090510ac@gleason> <20020319202137.U68606@backmaster.cdsnet.net> <20020320081439.74ca4530.steve@sohara.org> <20020319232049.W75496@nexus.root.com> <20020320190727.1cb65fac.steve@sohara.org> <20020320110647.A96231@nexus.root.com> <200203201928.g2KJSfZ85089@apollo.backplane.com> <20020320195801.GH52241@gromit.dlib.vt.edu>
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:Is this even the case when using >512-byte fragments?  In NetBSD, for
:example, you are limited to 1 TB filesystems when using 512-byte
:fragments, but up to 4 TB if using 2 KB fragments...
:
:Cheers,
:
:Paul.

    The UFS filesystem's block numbering is based on the fragment size,
    so UFS itself can handle bigger storage.  But the blocks still have
    to be converted to sector-sized numbers when the request hits the
    underlying disk device.  So, ultimately, we are limited by the physical
    sector size.

    There are also a few places in the kernel where we 'normalize' block
    numbers into DEV_BSIZE'd chunks.  DEV_BSIZE is 512 bytes.  This may or
    may not interfere with a filesystem talking to a large-sectored hard
    drive, I don't know.

					-Matt
					Matthew Dillon 
					<dillon@backplane.com>

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