Re: Raid-10 mount at startup always has problem

[Luca Berra <bluca@comedia.it>]

On Fri, Oct 26, 2007 at 03:26:33PM -0400, Doug Ledford wrote:
>On Fri, 2007-10-26 at 11:15 +0200, Luca Berra wrote:
>> On Thu, Oct 25, 2007 at 02:40:06AM -0400, Doug Ledford wrote:
>> >The partition table is the single, (mostly) universally recognized
>> >arbiter of what possible data might be on the disk.  Having a partition
>> >table may not make mdadm recognize the md superblock any better, but it
>> >keeps all that other stuff from even trying to access data that it
>> >doesn't have a need to access and prevents random luck from turning your
>> >day bad.
>> on a pc maybe, but that is 20 years old design.
>
>So?  Unix is 35+ year old design, I suppose you want to switch to Vista
>then?
unix is a 35+ year old design that evolved in time, some ideas were
kept, some ditched.

>> partition table design is limited because it is still based on C/H/S,
>> which do not exist anymore.
>> Put a partition table on a big storage, say a DMX, and enjoy a 20%
>> performance decrease.
>
>Because you didn't stripe align the partition, your bad.
:)
by default fdisk misalignes partition tables
and aligning them is more complex than just doing without.

>> >Oh, and let's not go into what can happen if you're talking about a dual
>> >boot machine and what Windows might do to the disk if it doesn't think
>> >the disk space is already spoken for by a linux partition.
>> Why the hell should the existance of windows limit the possibility of
>> linux working properly.
>
>Linux works properly with a partition table, so this is a specious
>statement.
It should also work properly without one.

>> If i have a pc that dualboots windows i will take care of using the
>> common denominator of a partition table, if it is my big server i will
>> probably not. since it won't boot anything else than Linux.
>
>Doesn't really gain you anything, but your choice.  Besides, the
>question wasn't "why shouldn't Luca Berra use whole disk devices", it
>was why I don't recommend using whole disk devices, and my
>recommendation wasn't based in the least bit upon a single person's use
>scenario.
If i am the only person in the world that believes partition tables
should not be required then i'll shut up.

>> On the opposite, i once inserted an mmc memory card, which had been
>> initialized on my mobile phone, into the mmc slot of my laptop, and was
>> faced with a load of error about mmcblk0 having an invalid partition
>> table.
>
>So?  The messages are just informative, feel free to ignore them.
but did not anaconda propose to wipe unpartitioned disks?

>The phone dictates the format, only a moron would say otherwise.  But,
>then again, the phone doesn't care about interoperability and many other
>issues on memory cards that it thinks it owns, so only a moron would
>argue that because a phone doesn't use a partition table that nothing
>else in the computer realm needs to either.
i don't count myself as a moron, what i am trying to say is that
partition tables are one way of organizing disk space, not the only one.

>> >Anyway, I happen to *like* the idea of using full disk devices, but the
>> >reality is that the md subsystem doesn't have exclusive ownership of the
>> >disks at all times, and without that it really needs to stake a claim on
>> >the space instead of leaving things to chance IMO.
>> Start removing the partition detection code from the blasted kernel and
>> move it to userspace, which is already in place, but it is not the
>> default.
>
>Which just moves where the work is done, not what work needs to be done.
and also permits to decide if it hat to be done or not.
>It's a change for no benefit and a waste of time.
the waste of time was having to put code in mdadm to undo partition
detection on component devices, where partition detection should not
have taken place.



-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
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