Re: [9fans] plan9 on vmware esx

[erik quanstrom <quanstro@quanstro.net>]

> Somehow my laptop gets by using 32-bit IP addresses regardless of
> whether it's on my home Ethernet, a dialup connection (rare these
> days in the U.S., still sometimes useful overseas), or on a
> wireless LAN.
>
> My landline phone and my cellular phone both use base-10 digits,
> and even the same number of digits!
>
>
> Hey, I know, let's name all disks by Ethernet MAC addresses :-)

if we did that, then we would never be able to have more
than one connection to the disk.  there needs to be a distinction
between the disks network address and the disk address if one
wishes to support multipathing for redundency or increased
bandwidth.

the sas wwn (also used in ata these days, btw) uniquely identifies
a target.  it's 8 bytes.  and looks for all the world like a mac address
with a 2-byte prefix (see contrib/quanstro oui).  one could identify
all scsi (modern) scsi drives by wwn and bury the topology inside
the scsi drivers.  that's typically what sas drives do.

this is all a bit convoluted.  aoe otoh has the advantage that
a lun's address is shelf.slot.  and the driver discovers mac addresses
on which the target is visable.  modulo driver bugs, one can
replug the network while doing io to a target and it just works.
one naturally gets multipathing by spreading out requests among
the mac addresses associated with a target.

- erik