Linux mdadm superblock question.
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From: Volker Armin Hemmann on 17 Feb 2010 13:30 On Mittwoch 17 Februar 2010, Nick Bowler wrote: > On 09:41 Wed 17 Feb , david(a)lang.hm wrote: > > for a distro that is trying to make one kernel image run on every > > possible type of hardware features like initramfs (and udev, modeules, > > etc) are wonderful. > > > > however for people who run systems that are known ahead of time and > > static (and who build their own kernels instead of just relying on the > > distro default kernel), all of this is unnessesary complication, which > > leaves more room for problems to creep in. > > Such people can easily construct an initramfs containing busybox and > mdadm with a shell script hardcoded to mount their root fs and run > switch_root. It's a ~10 minute jobbie that only needs to be done once. and even better when you don't have to do that one time job at all. btw, what about additional delay? 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: Nick Bowler on 17 Feb 2010 13:40 On 19:27 Wed 17 Feb , Volker Armin Hemmann wrote: > On Mittwoch 17 Februar 2010, Nick Bowler wrote: > > On 09:41 Wed 17 Feb , david(a)lang.hm wrote: > > > for a distro that is trying to make one kernel image run on every > > > possible type of hardware features like initramfs (and udev, modeules, > > > etc) are wonderful. > > > > > > however for people who run systems that are known ahead of time and > > > static (and who build their own kernels instead of just relying on the > > > distro default kernel), all of this is unnessesary complication, which > > > leaves more room for problems to creep in. > > > > Such people can easily construct an initramfs containing busybox and > > mdadm with a shell script hardcoded to mount their root fs and run > > switch_root. It's a ~10 minute jobbie that only needs to be done once. > > and even better when you don't have to do that one time job at all. But people who are building their own kernels are already doing a (much harder, imo) one time job of configuring their kernels. > btw, what about additional delay? It takes about half a second for mdadm to assemble my root array, is that what you're referring to? I assume that kernel auto-assembly is no faster, although I've never used it. Regardless, half a second isn't very long to wait. -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) -- 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: david on 17 Feb 2010 13:50 On Wed, 17 Feb 2010, Nick Bowler wrote: > On 19:27 Wed 17 Feb , Volker Armin Hemmann wrote: >> On Mittwoch 17 Februar 2010, Nick Bowler wrote: >>> On 09:41 Wed 17 Feb , david(a)lang.hm wrote: >>>> for a distro that is trying to make one kernel image run on every >>>> possible type of hardware features like initramfs (and udev, modeules, >>>> etc) are wonderful. >>>> >>>> however for people who run systems that are known ahead of time and >>>> static (and who build their own kernels instead of just relying on the >>>> distro default kernel), all of this is unnessesary complication, which >>>> leaves more room for problems to creep in. >>> >>> Such people can easily construct an initramfs containing busybox and >>> mdadm with a shell script hardcoded to mount their root fs and run >>> switch_root. It's a ~10 minute jobbie that only needs to be done once. >> >> and even better when you don't have to do that one time job at all. > > But people who are building their own kernels are already doing a > (much harder, imo) one time job of configuring their kernels. > >> btw, what about additional delay? > > It takes about half a second for mdadm to assemble my root array, is > that what you're referring to? > > I assume that kernel auto-assembly is no faster, although I've never > used it. Regardless, half a second isn't very long to wait. If you are aiming for a 5-second boot time it's 10% of your total boot time. That's a lot for a feature that's not needed. David Lang -- 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 17 Feb 2010 13:50 On Mittwoch 17 Februar 2010, Nick Bowler wrote: > On 19:27 Wed 17 Feb , Volker Armin Hemmann wrote: > > On Mittwoch 17 Februar 2010, Nick Bowler wrote: > > > On 09:41 Wed 17 Feb , david(a)lang.hm wrote: > > > > for a distro that is trying to make one kernel image run on every > > > > possible type of hardware features like initramfs (and udev, > > > > modeules, etc) are wonderful. > > > > > > > > however for people who run systems that are known ahead of time and > > > > static (and who build their own kernels instead of just relying on > > > > the distro default kernel), all of this is unnessesary complication, > > > > which leaves more room for problems to creep in. > > > > > > Such people can easily construct an initramfs containing busybox and > > > mdadm with a shell script hardcoded to mount their root fs and run > > > switch_root. It's a ~10 minute jobbie that only needs to be done once. > > > > and even better when you don't have to do that one time job at all. > > But people who are building their own kernels are already doing a > (much harder, imo) one time job of configuring their kernels. > > > btw, what about additional delay? > > It takes about half a second for mdadm to assemble my root array, is > that what you're referring to? > > I assume that kernel auto-assembly is no faster, although I've never > used it. Regardless, half a second isn't very long to wait. well at the moment it takes less than two seconds until init takes over. Adding .5 seconds is a lot. And loading the initrd and changing root isn't free either, true? I remember well all the noise in the past about making linux booting faster. So why slow it down with an initrd - especially if you can do without? 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: Nick Bowler on 17 Feb 2010 14:00
On 10:41 Wed 17 Feb , david(a)lang.hm wrote: > On Wed, 17 Feb 2010, Nick Bowler wrote: > > It takes about half a second for mdadm to assemble my root array, is > > that what you're referring to? > > > > I assume that kernel auto-assembly is no faster, although I've never > > used it. Regardless, half a second isn't very long to wait. > > If you are aiming for a 5-second boot time it's 10% of your total boot > time. That's a lot for a feature that's not needed. Only if the kernel auto-assembly takes zero time, which it obviously does not. -- Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/) -- 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/ |