RE: More on iSCSI boot

["Douglas Otis" <dotis@sanlight.net>]

Glen,

Regardless how robust you imagine iSCSI to be or become, it is of several
orders of greater complexity than TFTP or MTFTP, the preferred method of
obtaining a network boot image.  The initial concern being kicked around on
this thread was over the fact that each machine in a large enterprise would
need to be visited to initialize it with a shared secret for a secure boot
if diskless.  Trivial File Transfer Protocol is just that, trivial.  It is
well understood, can work within a slow and clumsy kernel, and can obtain a
secure initial boot image.  Use that boot image to then launch iSCSI.  If
you wish to include any option, use an existing professional management tool
combined with this initial boot image.  I see no reason to alter DHCP and I
would discourage the concept of using iSCSI for the initial boot in an
enterprise environment.

The advantage should be obvious.  Upgrades to this initial boot image is
possible without the need to revisit each machine.  The concern that this
then requires DHCP and TFTP network services for a boot to occur should be
weighed against the expense of updating each machine as iSCSI matures.  In
addition, as there is already a means to network boot, using the existing
standard provides an immediate solution that is stable and understood.  You
would not need to manage multiple methods for obtaining this initial boot
image.  A mode that captures this boot image where it is replayed until it
is rejected may provide better performance and make everyone happy as the
results would look the same.

Moving from direct attached drives should warrant this additional
consideration.  It should always be possible to set various defaults where
no intervention is needed to get the SCSI stack running into a boot device.
This should be possible for consumer items.  In which case even DHCP may not
be available.  That is a different problem all together.  Here you expect to
manage everything locally.  A floppy or CD may be used to create this
self-contained environment.  In this environment, DHCP is not likely
configurable to provide all the fun stuff being imagined.  Here you have a
need to get the code working through manual settings.

There is no justification to modify DHCP that I can see.

Doug