Date: Sat, 6 Jul 2002 17:33:50 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Bernd Walter <ticso@cicely5.cicely.de> Cc: Terry Lambert <tlambert2@mindspring.com>, Darren Pilgrim <dmp@pantherdragon.org>, ticso@cicely.de, freebsd-hackers@FreeBSD.ORG Subject: Re: How does swap work address spacewise? Message-ID: <200207070033.g670XoMJ064092@apollo.backplane.com> References: <20020705133837.GA513@HAL9000.wox.org> <20020705234126.GA12183@atrbg11.informatik.tu-muenchen.de> <3D2640A7.3EA2236B@pantherdragon.org> <20020706020656.GL48977@cicely5.cicely.de> <3D2762FE.9D9E0378@pantherdragon.org> <20020706220720.GG23704@cicely5.cicely.de> <3D277274.B5F3CE58@pantherdragon.org> <3D2776BE.A39A1110@mindspring.com> <20020706231346.GJ23704@cicely5.cicely.de> <200207062342.g66NgMri063859@apollo.backplane.com> <20020707001019.GK23704@cicely5.cicely.de>
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:On Sat, Jul 06, 2002 at 04:42:22PM -0700, Matthew Dillon wrote:
:> Negative block numbers are used by UFS to represent the indirect blocks
:> associated with a file, while positive block numbers represent the
:> contents of the file.
:
:I never saw any negative block numbers in on-disc structures.
:Now I wonder if it was just hidden behind macros.
:What is the reason to handle it that way?
:Do you have some code reference for homework?
LOGICAL block numbers, not physical block numbers.
:> These are logical block numbers, which are fragment-sized (1K typically).
:> So, 2^31 x 1K = 2TB.
:>
:> Physical block numbers are 512-byte sized, with a range of 2^32
:> in -stable. This also winds up being 2TB. So increasing the fragment
:> size does not help in -stable.
:
:It's a proven fact that there is a 1T limit somewhere which was
:explained with physical block numbers beeing signed.
:
:--
:B.Walter COSMO-Project http://www.cosmo-project.de
test1# vnconfig -e -s labels -r reserve -S 2t vn0
test1# disklabel -r -w vn0 auto
test1# disklabel vn0
...
bytes/sector: 4096
...
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
c: 536870912 0 unused 0 0 # (Cyl. 0 - 2097151)
Theoretically VN can create up to an 8TB virtual disk because the
sector size for a swap-backed VN device is 4K, but I'm not sure I
would want to test the theory.
With a regular file:
test1# vnconfig -e -s labels -T -S 2047g vn0 test.dat
test1# disklabel -r -w vn0 auto
test1# disklabel vn0
...
bytes/sector: 512
...
c: 4292870144 0 unused 0 0 # (Cyl. 0 - 2
test1# ls -la test.dat
-rw---xr-- 1 root wheel 2199023255552 Jul 7 00:31 test.dat
test1#
(of course, god help you if you tried to 'newfs' the above!)
-Matt
Matthew Dillon
<dillon@backplane.com>
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