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Re: [Xen-devel] pthread_mutex_lock() and Xenstored

To: Peter Teoh <htmldeveloper@xxxxxxxxx>
Subject: Re: [Xen-devel] pthread_mutex_lock() and Xenstored
From: Bastian Blank <bastian@xxxxxxxxxxxx>
Date: Sat, 15 Sep 2007 11:48:24 +0200
Cc: Vincent Hanquez <vincent@xxxxxxxxxxxxx>, "Daniel P. Berrange" <berrange@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On Sat, Sep 15, 2007 at 02:01:12PM +0800, Peter Teoh wrote:
>     * does databases need to be shareable across heterogeneous systems
> by a simple file copy across the network like SAMBA?

Most db files are not interchangable. And the xenstore db is usually
useless on another system. You want to define your own transfer format
if you want to do this and not rely on the db to support that.

>     * Can't use thread libraries as they conflict with LWP.

"Library for WWW in Perl"? Even wikipedia does not list a better match.
pthread is LSB and SUSv3. And with a proper db you can use fork if

>     * identifying the minimal amount of mapping operation needed, and
> possibly its corresponding hashing structures.
>     * and finally, to come up with the simplest design that meet all
> the requirements.
> Can Dan's CDB be a possible alternative candidate for our database
> design?   Please enlighten me :-).

Isn't CDB also read-only, aka needs to be rewritten on each write?
xenstored with tdb does this.

Usually I would say, bdb is a good choice for this usage. Supports
transactions, multiple reader. It is used by many things with large
writing frequency.


No one wants war.
                -- Kirk, "Errand of Mercy", stardate 3201.7

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