Re: Patch to multipath-tools 0.2.4

[christophe.varoqui@free.fr]

It sounds fair for scsi_id to try as hard as possible to generate a *really
unique* uid, thus the prefix.

In the context of multipath, do you suggest I introduce this prefix in the
fallback internal method or should I trim the scsi_id output ?

Subsidiary question : should I merge scsi_id in the multipath-tools tree for
klibc build ?

regards,
cvaroqui

Selon Patrick Mansfield <patmans@us.ibm.com>:

> On Mon, Jul 12, 2004 at 11:46:12PM +0200, christophe varoqui wrote:
> > On ven, 2004-07-09 at 18:00, Patrick Mansfield wrote:
> > > On Fri, Jul 09, 2004 at 05:50:23PM +0200, christophe varoqui wrote:
> > > > 
> > > > That, or a libscsiid ...
> > > > Do you plan to produce such a lib ?
> > > > 
> > > 
> > > No plans, but have thought about it. A callout is simpler and more
> > > flexible, maybe slower but that should not be a issue.
> > > 
> > ok, I got the callout working in my current tree.
> 
> Thanks for doing that work.
> 
> > before I release, I would like to report that scsi_id presents a strange
> > leading digit in its output.
> > In my case a wwid like 6005xxxxxxxxxxxx (32 char) becomes
> > 36005xxxxxxxxxxxx (33 char).
> > 
> > Note it's a bit annoying because the fallback get_evpd_wwid (in case
> > scsi_id is absent) rightfully reports 64 bit uuid, which is not
> > consistant with scsi_id reporting.
> > 
> > Can you explain this and give guidance ?
> 
> The first digit is the value of the "identifier type", looking at the SCSI
> primary commands draft spc3r19, the values in table 284, section 7.6.4.1,
> page numbered 312.
> 
> The different types of identifiers could in theory - though perhaps
> unlikely or maybe even impossible at this time - have overlapping name
> spaces. 
> 
> For example, the NAA IEEE extended has an 8 byte value (including the NAA
> type), as does the EUI-64 8 byte value (there are non 64 bit EUI-64
> values!?).
> 
> The page 0x83 "identifier type" is 8 bits, and so can never overlap with
> the scsi_id page 0x80 prefix of 0x53 ('S'), so the scsi_id page 0x80
> values can never overlap with page 0x83 values.
> 
> -- Patrick Mansfield
> 


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