Re: [PATCH 0/7] dlm: overview

From: David Lang
Date: Sat Apr 30 2005 - 23:17:27 EST

On Sat, 30 Apr 2005, Theodore Ts'o wrote:

the claim was that UUID's are unique and don't have to be assigned by the

I'm saying that in my experiance there isn't any standard or reliable way
to generate such a UUID and I'm asking for the people makeing the
claim to educate me on what I'm missing becouse a reliable UUID for linux
on all hardware would be extremely useful for many things.

How to reliably generate universally unique ID's have been well
understood for over twenty years, and is implemented on nearly every
Linux system for over ten. For more information I refer you to
doc/draft-leach-uuid-guids-01.txt in the e2fsprogs sources, and for an
implementation, the uuid library in e2fsprogs, which is used by both
GNOME and KDE. UUID's are also used by Apple's Mac OS X (using
libuuid from e2fsprogs), Microsoft Windows, more historically by the
OSF DCE, and even more historically by the Apollo Domain OS (1980 --
1989, RIP). Much of this usage is due to the efforts of Paul Leach, a
key architect at Apollo, and OSF/DCE, before he left and joined the
Dark Side at Microsoft.

Also, FYI the OSF/DCE, including the specification for generating
UUID's, was submitted by OSF to the X/Open where it was standardized,
who in turn submitted it to the ISO where it was approved as
Publically Available Specification (PAS). So technically, there *is*
an internationally standardized way of generating UUID's, and it is
already implemented and deployed on nearly all Linux systems.

thanks for the pointer. I wasn't aware of this draft (although from a reasonably short search it appears that this draft was allowed to expire, with no direct replacement that I could find)

I will say that this wasn't what I thought we was being talked about for cluster membership, becouse I assumed that the generation of an ID would be repeatable so that a cluster node could be rebuilt and re-join the cluster with it's old ID.

David Lang

There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies.
-- C.A.R. Hoare
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