Date: Mon, 27 Aug 2012 14:16:05 -0600 (MDT) From: Warren Block <wblock@wonkity.com> To: Kevin Oberman <kob6558@gmail.com> Cc: Erich Dollansky <erichfreebsdlist@ovitrap.com>, freebsd-stable@freebsd.org, Stefan Bethke <stb@lassitu.de>, Matt Smith <matt@xtaz.co.uk> Subject: Re: 9.1 RELENG_9 Unable to cleanly dismount root partition on shutdown Message-ID: <alpine.BSF.2.00.1208271356560.49435@wonkity.com> In-Reply-To: <CAN6yY1u1bJm_dBNKx4_rZkhgpevX6ovm1cyPeu5%2B929HSZWvZQ@mail.gmail.com> References: <2d4dfcb2637f4d0e9671899538b603d9@xtaz.co.uk> <67DFAA78-A9A2-49F9-9C29-CA5653ECE3C0@lassitu.de> <b98001dbe576eafcf4f4500e975680ec@xtaz.co.uk> <20120827172650.7e6a7685@AMD620.ovitrap.com> <c5c51c674a29c136f0d10a3fe936a6a0@xtaz.co.uk> <alpine.BSF.2.00.1208270750130.46223@wonkity.com> <78f8335e54e04f158609f0382afb8d4d@xtaz.co.uk> <alpine.BSF.2.00.1208271230360.48366@wonkity.com> <CAN6yY1u1bJm_dBNKx4_rZkhgpevX6ovm1cyPeu5%2B929HSZWvZQ@mail.gmail.com>
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On Mon, 27 Aug 2012, Kevin Oberman wrote: >> No obvious problems jumped out at me. Here are my notes: >> http://www.wonkity.com/~wblock/docs/html/disksetup.html >> >> The gpart version is halfway down. I really need to switch that around. > > Pretty good page, but I would really suggest that you also do either > 4k or 1M alignment on your partitions. If you don't and use a disk > with 4K blocks (internally), you will have terrible performance. You mean add the -a parameter for gpart? All that -a does is round partition starting blocks and sizes to even values. If the numbers given are already even multiples, it does nothing. The reason -a4k is not shown there is because until a few months ago, -a overrode -b. So # gpart add -t freebsd-ufs -l gprootfs -a4k -b 1M -s 2G da0 did not start that partition at 1M, but instead at the next even 4K block after the first 512K partition; block 1064 instead of block 2048, AFAIR. The fix to gpart (thanks to ae@) is in 9-stable and 9.1, but not earlier releases. Mentioned a little farther down in the article is that keeping additional partitions to even multiples of 1M or 1G size will keep them in alignment. > 1M is recommended by Microsoft and used by Windows, but seems a bit > excessive to me. Also by some Sun RAID controllers and other systems. 1M is a nice even multiple of a lot of common block sizes.
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