Hi Dimitri, On Thu, Feb 20, 2014 at 03:49:28PM +0000, Dimitri John Ledkov wrote: > This cycle a few things were done in mdadm & dmraid packages to > prepare for transition from dmraid to mdadm for a few formats that > mdadm supports.
> At the moment it trusty, mdadm has full support to assemble Intel > Matrix Raid and DDF fakeraid arrays, instead of dmraid. At the moment > however, mdadm codepath is disable via a kernel cmdline options > (nomdmonddf nomdmonisw) and thus if both mdadm and dmraid are present > in the initramfs dmraid will complete assembly. With or without kernel > options, dmraid completes assembly if mdadm is not present. Thus > existing upgrades continue to work as they are. > However to complete the upgrade, i would like remove the feature flag > and enable mdadm based assembly, such that installing mdadm migrates > systems using dmraid for Intel Matrix Raid and DDF fakeraids to mdadm. > But further changes are required, as the device names change when > moving from dmraid to mdadm, e.g.: > dmraid names: > * /dev/mapper/isw_cbhjgfachh_Volume1 > * /dev/mapper/isw_cbhjgfachh_Volume1p1 > * /dev/mapper/isw_cbhjgfachh_Volume1p2 > * /dev/mapper/isw_cbhjgfachh_Volume1p3 > become under mdadm: > * /dev/md/Volume1 > * /dev/md/Volume1p1 > * /dev/md/Volume1p2 > * /dev/md/Volume1p3 > Thus changes to /etc/fstab, and/or bootloader are required to look for > new places. > The question I have, is whether such migration should be done > automatically or left in the hands of the administrator (e.g. if mdadm > is not installed, dist-upgrade is performed no changes are required > and dmraid is continued to be used. If one installs mdadm, one would > also need to either disable mdadm-fakeraid assembly with kernel > cmdline options or adjust /etc/fstab & grub for the new names). I think we should definitely prefer such migration to be handled automatically. Have a look at the linux-base package in Debian: the postinst has been dropped from the Ubuntu package, but in Debian this is the package which handled the migration from /dev/hda to UUIDs. It's the logical place to insert other device name migrations, though it clearly would need some updating for new bootloader packages (FSVO "new" that includes "grub2" ;). Perhaps since this migration is specific to dmraid and mdadm it would make sense to move the migration code to mdadm itself, but hopefully this at least makes for a good starting point. Hope that helps, -- Steve Langasek Give me a lever long enough and a Free OS Debian Developer to set it on, and I can move the world. Ubuntu Developer http://www.debian.org/ [email protected] [email protected]
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