Date: Tue, 13 Nov 2012 07:30:30 +0100 From: Polytropon <freebsd@edvax.de> To: "Ronald F. Guilmette" <rfg@tristatelogic.com> Cc: freebsd-questions@freebsd.org Subject: Re: Advanced Format Drive ? Message-ID: <20121113073030.87bc0608.freebsd@edvax.de> In-Reply-To: <86166.1352787251@tristatelogic.com> References: <20121113065602.ee2310d7.freebsd@edvax.de> <86166.1352787251@tristatelogic.com>
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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. :-) -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...
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