Re: Patch to multipath-tools 0.2.4

[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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