Date: Wed, 22 Jul 2009 14:33:57 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Erik Trulsson <ertr1013@student.uu.se> Cc: Juli Mallett <jmallett@FreeBSD.org>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r195817 - head/usr.sbin/sysinstall Message-ID: <4A66F925.8000505@FreeBSD.org> In-Reply-To: <20090722111608.GA97528@owl.midgard.homeip.net> References: <200907220350.n6M3osaj030202@svn.freebsd.org> <4A66D0F4.4030108@FreeBSD.org> <eaa228be0907220157t6767adbdo77c1bf7144c1095b@mail.gmail.com> <4A66E9BE.2020603@FreeBSD.org> <20090722111608.GA97528@owl.midgard.homeip.net>
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Erik Trulsson wrote: > On Wed, Jul 22, 2009 at 01:28:14PM +0300, Alexander Motin wrote: >> Juli Mallett wrote: >>> On Wed, Jul 22, 2009 at 01:42, Alexander Motin<mav@freebsd.org> wrote: >>>> Colin Percival wrote: >>>>> Remove the "dedicated disk mode" partitioning option from sysinstall, in >>>>> both the disk partitioning screen (the 'F' key) and via install.cfg (the >>>>> VAR_DEDICATED_DISK option). This functionality is currently broken in 8.x >>>>> due to libdisk and geom generating different partition names; this commit >>>>> merely acts to help steer users away from the breakage. >>>> Is there any other way to not align FS block to the ugly legacy 63 >>>> sectors per track boundary with sysinstall now? I think RAIDs won't be >>>> happy. May be it would be better to fix it? >>> If you're interested in fixing this issue, you might want to look at >>> the need for compatibility names so that existing DD installs aren't >>> broken, and so DD installs work as-is without correcting libdisk's >>> expectations about slice/partition names for DD disks, which is pretty >>> invasive, too. Not breaking new installs by not letting users install >>> broken systems is the absolute bare minimum approach, and given the >>> late date and the lack of movement on the kernel side, I've been >>> advocating for it for a while. >>> >>> See this message and others in the thread for some background: >>> >>> http://lists.freebsd.org/pipermail/freebsd-geom/2009-June/003567.html >> Sorry, ENOTIME. I am not advocating DD mode, it is really a hack. Offset >> 0 is just an easiest choice to align FS. Instead, I would really like >> sysinstall to honor real disk geometry instead of fake one. > > "real disk geometry" ? How would sysinstall find that? As I have said, GEOM is able to provide such info to user-level when provider reports it. > Keep in mind that any disk geometry reported by disks is completely fake > these days and is just an attempt to fit the total number of blocks into > the limitations of the PC BIOS. > > In short the whole notion of 'disk geometry' is mostly obsolete these days > and ought to be avoided as far as possible. You are right about regular HDDs, but I am speaking mostly about RAID geometry: stripe (native block) size and it's offset. geom_stripe provides that kind of information, and I believe most of hardware RAIDs could also do it. Also it could be used for different SSD/FLASH storages, which have media erase block of more then one sector. Proper FS alignment could reduce number of media erases. mmcsd(4) driver reports SD/MMC card's erase block size there. -- Alexander Motin
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