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    SubjectRe: [linux-usb-devel] Re: /proc/scsi/map
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    patmans@us.ibm.com said:
    > I agree it would be nice to get the ID via user space, but it is not
    > that hard to get the ID, and trying the various SCSI INQUIRY pages
    > that supply the ID is not complicated.

    OK, how about some hardware scenarios:

    I've a scsi array (an LSI 6298) which has no WWN page (0x83) but does have a
    serial number in the VPD page. However, the VPD serial number is an
    identifier for the array *controller* and thus is the *same* for all the LUNs.
    For this beast I have to add in the LUN number to the VPD serial number to
    get a unique identifier per device. Worse, the LSI 6298 is multi path. Now I
    get a different "unique" identifier depending on path (because different
    controllers give different VPD serial numbers), so if I want to identify it
    uniquely, I have to use some property of the LUN, like partion UUID.

    Or, what about an old 8 bit EMC symmetrix. They have no WWN page and they
    embed both a LUN and a *path* identifier in the VPD serial number. To get the
    globally unique ID for this one, I have to strip off the path part.

    > FYI the various SCSI ID pages and such are described in the SCSI
    > primaray command for example the following:

    > ftp://ftp.t10.org/t10/drafts/spc3/spc3r07.pdf

    Ah, but that's the scsi-3 spec which (finally) cleaned up this unique name
    business. However, for SCSI-2 and before, it was an unholy mess, as the two
    examples above illustrate. I agree that for all modern devices which are
    SCSI-3 SPC compliant, then just asking for the WWN page probably works. The
    question is what to do about all the legacy hardware out there?

    James


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