On Thu, 19 Apr 2012 10:38:23 +1000 NeilBrown <neilb@xxxxxxx> wrote: > On Wed, 18 Apr 2012 18:18:33 -0600 Ken Gunderson > <kgunders@xxxxxxxxxxxx> wrote: > > > On Tue, 17 Apr 2012 14:40:10 -0600 > > Ken Gunderson <kgunders@xxxxxxxxxxxx> wrote: > > > > Apologies for following my own post but I guess should elaborate... > > > > > Hello: > > > > > > I'm wanting to set up a new md root lvm based configuration and > > > after reading various docs am confused about how I should be > > > going about this. My intent is to have mirrored /boot and swap > > > partitions and a raid10 / partition with LVM. > > > > > > Issue #1: gpt is recommended over mbr based partitioning for new > > > installs, even on BIOS based systems (presuming these BIOS will > > > boot gpt, wh/mine do). Auto-assemble is not recommended for new > > > installations (my understanding is that it is not necessary with > > > initramfs) so I presume I should be specifying partition type DA. > > > However, while gdisk et.al. allow for selecting type FD, they do > > > not offer DA as an option. > > > > Per <http://www.rodsbooks.com/linux-fs-code.html>, Linux ignores > > partition type codes. Yet per man mdadm: > > > > "When creating a partition based array, using mdadm with > > version-1.x metadata, the partition type should be set to 0xDA (non > > fs-data). This type selection allows for greater precision since > > using any other [RAID auto-detect (0xFD) or a GNU/Linux partition > > (0x83)], might create prob‐ lems in the event of array recovery > > through a live cdrom." > > > > So which is it? Does partition type code matter to md/mdadm or not? > > Both. Neither. > > md does handle 0xFD partitions a bit differently, but I recommend not > using that feature. > Other than that md igores them. mdadm ingores them completely. > > But other tools - typically installers - might pay some attention to > them. Using 0xDA discourages such tools from mishandling them. Thanks for the clarification. > > > Issue #2: Is there any reason to prefer 1.0 vs. 1.2 metadata? I > > > can use either grub2 or Syslinux boot loaders. My understanding > > > is that Syslinux supports the former while Grub2 supports 1.2. > > > All other things being equal, I'd prefer to use Syslinux. Unless > > > there is some technical reason to favor 1.2 metadata and/or Grub2. > > > > > > So what would be best practices recommended way to proceed here? > > > > The reason I ask is that I bring such a configuration online on > > Archlinux by following these instructions: > > > > <https://wiki.archlinux.org/index.php/Software_RAID_and_LVM> > > > > But I'll be damned if I can recover from failed drive simulations - > > at least reliably, as sometimes it works while others not - so I'm > > just trying to rule out potential variables here. > > > > Thanks-- Ken > > > > Any reason for preferring one of 1.0 and 1.2 is out side of md. > > Maybe you want to be able to mount one half of a RAID1 > independently. You need 1.0 for that. Maybe you want to ensure that > never happens. Then 1.2 is better. Maybe your boot loaded only works > with one. Then the choice is clear. Well, this only pertains to /boot partition, so there's nothing to stop one from mixing and matching, e.g. Syslinux using 1.0 metadata for RAID1 /boot and 1.2 metadata for RAID10 swap and root devices, no? Or is this not advisable? Thanks-- Ken -- Ken Gunderson <kgunders@xxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
