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

[Bill Nottingham <notting redhat com>]

Hans de Goede (hdegoede redhat com) said: 
>> ... 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.

Sure, you have to keep dmraid around for some legacy BIOSes, but...

> 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.

This means that for users of a particular BIOS, you get to write "If X, do
Y. If A, do B" sort of docs, which are always bad. You get to wire
distro-specific magic into anaconda, rc.sysinit, mkinitrd, dracut, etc.,
etc. You ensure that the old, dead, no longer maintained support for
whichever tool is non-default for a format can never be turned off. And
you require the user to pass magic options anyway.

It's best to just cut the cord for people who need to migrate. It's a
one-time user cost, as opposed to an ongoing maintenance cost.

Bill