Re: Raid-10 mount at startup always has problem

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:

quoted

On Thu, Oct 25, 2007 at 02:40:06AM -0400, Doug Ledford wrote:

quoted

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.

quoted

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.

quoted

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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.

quoted

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.

quoted

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.

quoted

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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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