Date: Tue, 24 May 2011 11:46:06 -0600 From: Warner Losh <imp@bsdimp.com> To: Marcel Moolenaar <xcllnt@mac.com> Cc: "Andrey V. Elsukov" <bu7cher@yandex.ru>, Andriy Gapon <avg@FreeBSD.org>, freebsd-geom@FreeBSD.org Subject: Re: [RFC] Remove requirement of alignment to track from MBR scheme Message-ID: <2FCA1E3C-E11C-46C9-A41B-E5DF4D8BA1FC@bsdimp.com> In-Reply-To: <D7C4124D-A690-4960-B141-594C7E2BE792@mac.com> References: <4DDA2F0B.2040203@yandex.ru> <D75B2856-D9D8-4BA3-BC54-8258610CEA06@xcllnt.net> <9ED563AB-7B35-40F4-A33E-015317858401@bsdimp.com> <4DDB5375.6050004@FreeBSD.org> <D7C4124D-A690-4960-B141-594C7E2BE792@mac.com>
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On May 24, 2011, at 10:35 AM, Marcel Moolenaar wrote: >=20 > On May 23, 2011, at 11:43 PM, Andriy Gapon wrote: >=20 >> on 23/05/2011 20:38 Warner Losh said the following: >>>=20 >>> On May 23, 2011, at 10:35 AM, Marcel Moolenaar wrote: >>>> I think we've had enough rushed and ill thought-out changes going >>>> in already and I can see that not aligning MBR partitions on a = track >>>> boundary is potentially perceived as a PITA violation. >>=20 >> _PITA_ violation? :-) >> As to POLA - yeah, I can see people getting astonished that finally = FreeBSD got >> its sh*t together and did the right thing, years after all other OSes = (even >> Winddows) had done it. >=20 > :-) >=20 > Well, I just initialized a USB stick on my Mac and I see that it > still adheres to some notion of geometry: >=20 > : > ugen3.2: <ITE Tech Inc.> at usbus3 > umass0: <ITE Tech Inc. USB FLASH STORAGE, class 0/0, rev 2.00/2.00, = addr 2> on usbus3 > da0 at umass-sim0 bus 0 scbus0 target 0 lun 0 > da0: <Simple Bonzai Xpress 2.20> Removable Direct Access SCSI-2 device=20= > da0: 1.000MB/s transfers > da0: 499MB (1023484 512 byte sectors: 64H 32S/T 499C) > GEOM: da0s1: EBR has non empty bootcode. > GEOM: msdosfs/MAC: EBR has non empty bootcode. > marcelm-server% gpart show da0 > =3D> 32 1023424 da0 MBR (499M) > 32 31 - free - (15k) > 63 1023372 1 fat32 (499M) > 1023435 21 - free - (10k) does fdisk report the same thing? When I was poking, the 16GB stick I = have reported something similar to this via gpart show, but showed there = was nothing at the end when reported with fdisk. > gpart synthesized a 64 head, 32 sectors/track geometry, which > is not the same as the 63 sectors/track that Mac synthesized. > Yes, this demonstrates the bogosity of geometry, but it also > shows that it still exists. It still exists, but on the other hand it isn't *that* useful... > All I'm saying: be careful. Agreed. But the care should be on the creation side, not on the = interpretation side. In general, we should believe what the MBR says = and not do the kinds of rounding we do with creation. Also, I think = that we should allow non-aligned to fake geometry creations if the user = desires (or maybe even go so far as to make that the default and have = alignment forcing be a requested behavior). Warner > --=20 > Marcel Moolenaar > xcllnt@mac.com >=20 >=20 >=20 >=20
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