Re: RFC: proposal for handling isw dmraid -> mdraid upgrade path

[Hans de Goede <hdegoede redhat com>]

Hi,

On 06/30/2009 11:08 PM, Bill Nottingham wrote:
> Hans de Goede (hdegoede redhat com) said:
> > I've been thinking about $SUBJECT lately, and I would like to propose the
> > following way to handle this:
> >
> > 1) Make the use of mdraid or dmraid for BIOS-raid supported by both
> >     configurable both in anaconda (it already is) and in the installed OS
> >     (so in relevant udev rules and / or in rc.sysinit).
> >
> >     anaconda will have a cmdline option to override the defaults, and the
> >     installed system will have a /etc/sysconfig/biosraid file, with a
> >     single setting:
> >     PREFERRED_BIOSRAID_HANDLER
> >
> >     Which can be either dmraid or mdraid
>
> ... why do we want to do this? Supporting two entirely separate code paths
> for a single device is *bad*.

Because we will need both code paths anyways as for some bios-raid's mdraid
will be the preferred method, while others will only be supported by dmraid.

Given that we need the 2 code paths anyways, making which one to use
configurable when both support the type of bios-raid is much easier, and
certainly much less error prone, then trying to handle device name changes
when upgrading.

Regards,

Hans