Linux mdadm superblock question.
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From: david on 14 Feb 2010 02:30 On Sat, 13 Feb 2010, Michael Evans wrote: > On Sat, Feb 13, 2010 at 5:51 PM, Volker Armin Hemmann > <volkerarmin(a)googlemail.com> wrote: >>> 0.90 has a very bad problem, which is that it is hard to distinguish >>> between a RAID partition at the end of volume and a full RAID device. >>> This is because 0.90 doesn't actually tell you the start of the device. >>> >>> Then, of course, there are a lot of limitations on size, number of >>> devices, and so on in 0.90. >> >> but it is the only format supporting autodetection. >> >> So - when will autodetection be introduced with 1.X? And if not, why not? >> >> All I found was 'autodetection might be troublesome' and nothing else. >> �But dealing with initrds is troublesome too. Pure evil even. >> >> Gl?ck Auf, >> Volker >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-raid" in >> the body of a message to majordomo(a)vger.kernel.org >> More majordomo info at �http://vger.kernel.org/majordomo-info.html >> > > I remember hearing that 1.x had /no/ plans for kernel level > auto-detection ever. That can be accomplished in early-userspace > leaving the code in the kernel much less complex, and therefore far > more reliable. > > In other words, 'auto-detection' for 1.x format devices is using an > initrd/initramfs. hmm, I've used 1.x formats without an initrd/initramfs (and without any conifg file on the server) and have had no problem with them being discovered. I haven't tried to use one for a boot/root device, so that may be the difference. David Lang
From: Michael Evans on 14 Feb 2010 03:40 On Sat, Feb 13, 2010 at 11:21 PM, <david(a)lang.hm> wrote: > On Sat, 13 Feb 2010, Michael Evans wrote: > >> On Sat, Feb 13, 2010 at 5:51 PM, Volker Armin Hemmann >> <volkerarmin(a)googlemail.com> wrote: >>>> >>>> 0.90 has a very bad problem, which is that it is hard to distinguish >>>> between a RAID partition at the end of volume and a full RAID device. >>>> This is because 0.90 doesn't actually tell you the start of the device. >>>> >>>> Then, of course, there are a lot of limitations on size, number of >>>> devices, and so on in 0.90. >>> >>> but it is the only format supporting autodetection. >>> >>> So - when will autodetection be introduced with 1.X? And if not, why not? >>> >>> All I found was 'autodetection might be troublesome' and nothing else. >>> �But dealing with initrds is troublesome too. Pure evil even. >>> >>> Gl?ck Auf, >>> Volker >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in >>> the body of a message to majordomo(a)vger.kernel.org >>> More majordomo info at �http://vger.kernel.org/majordomo-info.html >>> >> >> I remember hearing that 1.x had /no/ plans for kernel level >> auto-detection ever. �That can be accomplished in early-userspace >> leaving the code in the kernel much less complex, and therefore far >> more reliable. >> >> In other words, 'auto-detection' for 1.x format devices is using an >> initrd/initramfs. > > hmm, I've used 1.x formats without an initrd/initramfs (and without any > conifg file on the server) and have had no problem with them being > discovered. I haven't tried to use one for a boot/root device, so that may > be the difference. > > David Lang Yes, that is the difference. You must have a more traditional simple block device and filesystem drivers compiled in. You have no need for extra drivers or higher level device detection and evaluation (with user-set policies to determine operation). Anything past root-fs mount can happen in normal user-space before logins are enabled. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Volker Armin Hemmann on 14 Feb 2010 13:50 On Sonntag 14 Februar 2010, you wrote: > > In other words, 'auto-detection' for 1.x format devices is using an > initrd/initramfs. which makes 1.x format useless for everybody who does not want to deal with initrd/initramfs. Gl�ck Auf, Volker -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: John Robinson on 14 Feb 2010 14:20 On 14/02/2010 18:40, Volker Armin Hemmann wrote: > On Sonntag 14 Februar 2010, you wrote: > >> In other words, 'auto-detection' for 1.x format devices is using an >> initrd/initramfs. > > which makes 1.x format useless for everybody who does not want to deal with > initrd/initramfs. True, but afaik every distro uses an initrd/initramfs and bundles tools making it easy to manage and customise them, so what's the problem? Cheers, John. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Henrique de Moraes Holschuh on 14 Feb 2010 14:40
On Sat, 13 Feb 2010, Michael Evans wrote: > I remember hearing that 1.x had /no/ plans for kernel level > auto-detection ever. That can be accomplished in early-userspace > leaving the code in the kernel much less complex, and therefore far > more reliable. Yes, it is far more reliable kernel side, if only because it doesn't do anything. But the userspace reliability is _not_ good. initrds are a source of problems the moment things start to go wrong, and that's when they are not the problem themselves. And the end result is a system that needs manual intervention to get its root filesystem back. In my experience, every time we moved critical codepaths to userspace, we ended up decreasing the *overall* system reliability. -- "One disk to rule them all, One disk to find them. One disk to bring them all and in the darkness grind them. In the Land of Redmond where the shadows lie." -- The Silicon Valley Tarot Henrique Holschuh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |