Date: Tue, 25 Oct 2011 13:20:10 GMT From: Warren Block <wblock@wonkity.com> To: freebsd-sysinstall@FreeBSD.org Subject: Re: bin/161720: bsdinstall(8): partition editor does not put partitions on even 4K boundaries Message-ID: <201110251320.p9PDKAbX031181@freefall.freebsd.org>
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The following reply was made to PR bin/161720; it has been noted by GNATS. From: Warren Block <wblock@wonkity.com> To: Dennis Yusupoff <dyr@smartspb.net> Cc: bug-followup@FreeBSD.org Subject: Re: bin/161720: bsdinstall(8): partition editor does not put partitions on even 4K boundaries Date: Tue, 25 Oct 2011 07:17:24 -0600 (MDT) On Tue, 25 Oct 2011, Dennis Yusupoff wrote: > While I agree with you in need of aligning [first] partition, I'd like > to behold, that gpart show size in blocks, not in megabytes, so to align > partition to 1 mbyte on 4K-align HDDs you might execute "gpart add -b > 2048 -s 64K -t freebsd-boot ada0" ( 2048 blocks * 4096 kbytes = 8 Mbyte, > in case of "plain" HDD 2048 blocks * 512 bytes = 1 Mbyte, which, I > think, is a pretty good). The -b option to 'gpart add' also accepts a size like "1M", so 'gpart add -t freebsd-ufs -b 1M ...' should work on any drive with a block size all the way up to 1M. Tested and works on 512-byte drives, but I have not tested it on a 4K drive. There's also the -a option, which attempts to align partitions to the value given. '-a 4096' should work on both 512-byte and 4k-byte drives. (bsdinstall's partition editor and wizard do not run gpart(8) but make lower-level calls to libgeom. Still, the functionality of the -a or -b options could be duplicated.) > Moreover, I don't see why freebsd-boot partition should be more than > 512K, if even 64K are currently just enough for FreeBSD. Looks like old > and famous Bill Gates's sentence, I know, but however :) FreeBSD bootcode has problems with a freebsd-boot partition larger than 512K, so that's the current limit. However, starting the first filesystem partition at 1M works for both alignment and compatibility with other systems. From the -current mailing list: http://lists.freebsd.org/pipermail/freebsd-current/2011-September/027547.html http://lists.freebsd.org/pipermail/freebsd-current/2011-September/027548.html http://lists.freebsd.org/pipermail/freebsd-current/2011-September/027550.html http://lists.freebsd.org/pipermail/freebsd-current/2011-September/027563.html http://lists.freebsd.org/pipermail/freebsd-current/2011-September/027626.html
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