Date: Tue, 13 Nov 2012 08:09:15 +0000 From: Arthur Chance <freebsd@qeng-ho.org> To: Polytropon <freebsd@edvax.de> Cc: freebsd-questions@freebsd.org, "Ronald F. Guilmette" <rfg@tristatelogic.com> Subject: Re: Advanced Format Drive ? Message-ID: <50A2002B.9040003@qeng-ho.org> In-Reply-To: <20121113073030.87bc0608.freebsd@edvax.de> References: <20121113065602.ee2310d7.freebsd@edvax.de> <86166.1352787251@tristatelogic.com> <20121113073030.87bc0608.freebsd@edvax.de>
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On 11/13/12 06:30, Polytropon wrote: > On Mon, 12 Nov 2012 22:14:11 -0800, Ronald F. Guilmette wrote: >> Which "partitions" need to be aligned to the 4KB boundaries? >> The FreeBSD ones, the MBR ones, or both? > > The partitions, all of them. :-) > > For MBR partitions, the "DOS primary partitions", which are > slices, you typically only need one if you want to stay in > compatibility mode. For dedicated mode, you don't need it. > > The slice typically starts in sector 63 and occupies the > space until the end of the device. > > The partitions within the slice should have sizes of > multiples of 1 MB or 1 GB (which makes them multiples > of 4k easily). > > See: > http://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html > > Even though the handbook elaborates on the GPT approach, it > will work with traditional disklabel partitioning too. > > Note that 4k = 8 x 512 byte, and so 64 sectors would be a > good alignment "grid", while 63 sectors is not. That implies > that in case you use fdisk to create a slice holding your > partitions, try to make it start at sector 64 (63 would > have been the default). > > After that, use bsdlabel to create the partitions inside > the slice as you want. Make them multiples of 1M or 1G, > that should be no big deal because disks are big and cheap > today. :-) > > You can then easily use newfs with the -f parameter: > > newfs -U -f 4096 <device> > > This will make sure the proper fragment size will be applied > upon formatting the created partitions. > > Also see: > http://www.wonkity.com/~wblock/docs/html/disksetup.html > > As I have limited experience, anyone having more practical > experience with this matter is welcome to comment. :-) According to the manual as of 9.0-RELEASE the default fragment and block sizes for newfs are 4k and 32k, so provided your partitions/slices are 4k aligned everything Should Just Work. Before 9.0 fragments and blocks were 2k and 16k which doesn't play so well with 4k drives.home | help
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