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Date:      Fri, 21 Jul 2000 15:03:27 -0700 (PDT)
From:      Matthew Jacob <mjacob@feral.com>
To:        wilko@freebsd.org
Cc:        freebsd-arch@freebsd.org
Subject:   Re: How much do we need the all-singing, all-dancing devfs?
Message-ID:  <Pine.BSF.4.05.10007211457470.8451-100000@semuta.feral.com>
In-Reply-To: <20000721233903.A21976@freebie.demon.nl>

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> These are 64 bit WWNs. For example the CPQ HSGxx StorageWorks arrays
> present a 128 bit extended WWN for each of the LUNs they can present to
> the FC-AL/fabric they are connected to. A total of 128 LUNs can be presented
> via 2 host port pairs (a pair of ports acts as a failover pair in case one
> has redundant array controllers; of each controller one port is part of one
> pair). 

The FC cards only support 64 bit WWNs- these are part of the class 3 service
paramaters. The 128 bit WWNs *may* be available- but you have to use VPD info
to get at them- all of which is do-able and should be one.

> 
> Serial numbers (IIRC) that are presented by a LUN are all the same: the ser#
> of the HSG raid controller. And are therefore quite useless to the problem
> at hand.

That's why there's a lun qualifier after the serial number. The same thing,
btw, applies to 64 bit WWNs- they're for target, not the lun.


> So, I think it would be nice if 128 bit WWN could also be handled.

Yes, I agree.



> A, very desirable IMO, side effect is that once this is done correctly one
> can use the information for use in a dual-rail driver. For HA systems having
> a dual connection to a RAID box becomes rather common these days. Using 
> the WWNs it is relatively easy to spot multiple paths to a single LUN/disk.

Yes! Yes! Yes! Exacto-mundo!

> ...
> The problem I see is the fact that I have yet to meet someone who can 
> correctly transcribe 64 bit numbers, let alone 128bit ones.. :-( But there
> is only so much you can do about that problem.

Yes- this is indeed a problem. But I would view this as just the need for a
tool- possibly Tcl/Tk with X extensions, to allow you to do volume selection
which would be responsible for adding things to fstab.

But do people have any plus/minus feelings about linking mount with libcam so
it can try and translation information? I also feel that it would be better if
this were less device class specific, but maybe that waits the full devfs
(which I don't expect to see in 5.0).

-matt





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