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List:       osdl-device-naming
Subject:    Re: [Device_naming] Re: Re: Novell/SUSE Device Naming Proposal
From:       Ihno Krumreich <ihno () suse ! de>
Date:       2004-07-24 2:32:08
Message-ID: 20040724023208.GA10899 () wotan ! suse ! de
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On Fri, Jul 23, 2004 at 04:20:54PM -0700, Timothy D. Witham wrote:
> On Fri, 2004-07-23 at 14:17, Bill Nottingham wrote:
> > Ihno Krumreich (ihno@suse.de) said: 
> > > > > - What we're trying here is to establish a common suggestion about how a 
> > > > > persistent device naming scheme could be done. If there are areas/ideas 
> > > > > which are wrong and/or could be done better, please make suggestions how 
> > > > > it could be improved. Just stating 'this is crap' is not very helpful. 
> > > > > I'm not trying to impose a solution, i'm trying to get a discussion started.
> > > > 
> > > > Well, one problem is that by-path is generally not persistent; it's very
> > > > easy to change the path without changing the actual device. Hence, I'm
> > > > not sure by-path buys you much in a persitsent naming scheme.
> > > 
> > > It is of course easy to change the path without changing the actual device.
> > > But in this case someone has active changed the hardware and is NOT
> > > surprised when the names of the disks change.
> > 
> > 'In this case'? All I see is a proposed scheme for persistent naming;
> > it doesn't specify 'use this in this usage case', 'use this for this other'.
> > 
> > Moreover, I don't see how you tell someone 'depending on your future
> > potential usage model, access your devices as <A> or <B>'.

The proposel offers two possibilities: by-path and by-id. And depending
on the usage case one has advantages over the other. 

> 
>    That is my issue.  It doesn't meet my definition of persistent
> naming.  For example if I have two SCSI channels each with 4
> drives on them and I add 2 new drives - one to each channel it seems
> to me that everything past that 1st new drive on the 1st channel
> would have a new name.  If I'm wrong then I'm really not understanding
> your terminology.
> 

if the old scheme (aka /dev/sda, /dev/sdb ...) is used exact that happens.
if you use by-path the second channel has its own path, so a additional drive
on the first channel does not effect the names of the drives of the second
channel.

Ihno

-- 
Best regards/Mit freundlichen Grüßen

Ihno Krumreich

"Never trust a computer you can lift."
--
Ihno Krumreich            ihno@suse.de
SuSE Linux AG             Projectmanager S390 & zSeries
Maxfeldstr. 5             +49-911-74053-439
D-90409 Nürnberg          http://www.suse.de
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