Date: Wed, 23 Feb 2011 09:37:05 -0600 From: "Mark Felder" <feld@feld.me> To: freebsd-stable@freebsd.org Subject: Re: 3TB disc and block alignment Message-ID: <op.vrc4b1kd34t2sn@tech304> In-Reply-To: <20110221161637.GR34314@home.opsec.eu> References: <20110217115653.GH34314@home.opsec.eu> <AANLkTi=QMXvFtTyY9BUGg56VtTuac3G_0LnXaVboJQQz@mail.gmail.com> <20110217124515.GI34314@home.opsec.eu> <4D5D1D10.7010000@digsys.bg> <20110217180140.GL66849@dan.emsphone.com> <20110217204643.GJ34314@home.opsec.eu> <37576665@h30.sp.ipt.ru> <20110221161637.GR34314@home.opsec.eu>
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On Mon, 21 Feb 2011 10:16:37 -0600, Kurt Jaeger <lists@c0mplx.org> wrote: > Hi! > >> > Hmm, wasn't the issues with 3T drives, that they internally use >> > 4K blocks and emulate 512 and that therefore 8 block alignments >> > are an performance issue ? >> Hi guys, I'd just like to jump on this train real quick since I have a related question with alignment. I've been building new Virtual Machine templates lately because I recently learned that our SAN which we access over iSCSI uses 64K blocks and the default FreeBSD install starts a filesystem on sector 63 (512K sectors). This would be misaligned for most I/O transactions. As a result, I updated our internal documentation for FreeBSD standards to be 64K aligned by manually installing FreeBSD with GPT and making the FreeBSD-boot partition 64K in size: Fixit# gpart create -s gpt da0 Fixit# gpart add -t freebsd-boot -s 64K da0 Fixit# gpart add -t freebsd-swap -s 2G -b 2048 da0 Fixit# gpart add -t freebsd-ufs da0 Fixit# gpart bootcode -b /dist/boot/pmbr -p /dist/boot/gptboot -i 1 da0 At the time, the examples I found used -s 64K for the freebsd-boot partition which starts the next partition/filesystem on the next 64K block which would be aligned for our purposes. However, I have been seeing -s 1024K or larger which is also 64K aligned, but just larger. Am I shooting myself in the foot by not going ahead and aligning with -s 1024K or -s 2048K right now? Thanks for your opinions, Mark
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