Date: Wed, 23 May 2012 21:49:15 -0700 From: Tim Kientzle <tim@kientzle.com> To: Warren Block <wblock@wonkity.com> Cc: freebsd-hackers@freebsd.org, Matthias Apitz <guru@unixarea.de> Subject: Re: proper newfs options for SSD disk Message-ID: <CF851064-F78F-44AF-B562-32012E4DC043@kientzle.com> In-Reply-To: <alpine.BSF.2.00.1205220837500.51493@wonkity.com> References: <alpine.BSF.2.00.1205182209010.9350@wojtek.tensor.gdynia.pl> <4fb7dfd6.736a980a.186d.ffff902f@mx.google.com> <20120519180901.GA1264@tiny> <4fb7e819.6968700a.7a7f.ffff9153@mx.google.com> <20120522061734.GA1210@tiny> <alpine.BSF.2.00.1205220731070.51493@wonkity.com> <20120522134846.GA2274@tiny> <alpine.BSF.2.00.1205220837500.51493@wonkity.com>
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On May 22, 2012, at 7:40 AM, Warren Block wrote: > On Tue, 22 May 2012, Matthias Apitz wrote: >=20 >> El d=EDa Tuesday, May 22, 2012 a las 07:42:18AM -0600, Warren Block = escribi=F3: >>=20 >>> On Tue, 22 May 2012, Matthias Apitz wrote: >>>=20 >>>> El d=EDa Sunday, May 20, 2012 a las 03:36:01AM +0900, = rozhuk.im@gmail.com escribi=F3: >>>>>=20 >>>>> Do not use MBR (or manually do all to align). >>>>> 63 - not 4k aligned. >>>>=20 >>>> To create the above shown partition layout I have not used = gpart(8); I >>>> just said: >>>>=20 >>>> # fdisk -I /dev/ada0 >>>> # fdisk -B /dev/ada0 >>>>=20 >>>> ... >>>> What is wrong with this procedure? >>>=20 >>> The filesystem partitions end up at locations that aren't even = multiples >>> of 4K. This can reduce performance. How much probably depends on = the >>> SSD. >>=20 >> But this is then rather a bug in fdisk(8) and not a PEBKAC, or? :-) >=20 > A bug in the design of MBR. Which probably can be forgiven, = considering when it was created and the other problems with it. :) >=20 > gpart's alignment option can be used with MBR slices and bsdlabel = partitions. GPart's alignment option doesn't work for MBR slices. It rounds to the requested alignment, and then rounds again to the track size, which defaults to 63 sectors. I'm not convinced this is a bug in the design of MBR. I don't think anything in the MBR design requires that partitions be track-aligned. Tim
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