Re: Superblock V 1.2

[John Robinson <john.robinson@anonymous.org.uk>]

On 09/11/2010 16:35, Martin Cracauer wrote:
> John Robinson wrote on Sun, Nov 07, 2010 at 09:39:03PM +0000:
[...]
>> That's the other difference between 0.90 and 1.x metadata. In-kernel
>> auto-assembly is only available for 0.90, and Neil Brown has made it
>> clear that there will never be in-kernel auto-assembly for 1.x, and
>> explained at length why. You need mdadm to start 1.x arrays, in your
>> initrd if your root filesystem is on such an array. All modern distros
>> create suitable initrds automatically. We are moving towards having
>> array assembly handled by udev invoking mdadm as devices are discovered.
>
> That's good it know.  I still think that udev is a plot to destroy
> Linux as we know it so I guess I'm gonna recreate this particular
>   array :-)
>
> What do you do if you plug in a couple harddrives that have arrays on
> them that you do not want assembled? Right now you just set them to a
> partition type other than autodetect and you are good.

You can still do that, but the "right" way to do it (I think) is to use 
the AUTO keyword and only to include the arrays you want assembled at 
boot time in the mdadm.conf that goes into the initrd.

> What do you do when udev maintainers in distributions screw up and
> replace good udev entires with bad ones? That happened to me
> repeatedly and is the major reason for the attitude above.

Oh dear, you've had a bad experience there then. I like udev. I disliked 
the old huge /dev with gazillions of entries for devices you don't have, 
and you still ended up using MAKEDEV or mknod whenever you added 
something new. I did say "moving towards" because udev-based assembly 
isn't 100% there yet, and I don't think any distros are trying to use 
it. But the other great thing we will get with udev is hotplugging, 
including the option to configure in advance auto-rebuilding of arrays, 
something that hardware RAID adapters have always had but we still don't 
for software RAID.

Cheers,

John.