Finding boot devices on a SAN
relliott at hobbit.eng.hou.compaq.com
Thu May 11 17:56:19 PDT 2000
* From the T10 Reflector (t10 at t10.org), posted by:
* relliott at hobbit.eng.hou.compaq.com (Robert Elliott)
There doesn't seem to be a standard way for an operating system
to find its boot images/boot volumes on disk drives scattered
throughout a SAN. Today, boot code is forced to do
a) store disk target/LUN addresses in non-volatile memory
on the host adapter card
b) store disk target/LUN addresses in non-volatile memory
on the system
c) read from all the disk drives that are found, looking
for signatures previously written
Option a) makes replacing failed host adapters difficult.
It's not practical to move a ROM from one board to another.
Option b) is not practical because not all systems provide
such storage, and there don't seem to be industry-standard
ways for accessing such storage (at least in the x86 space).
Option c) wastes a lot of time and consumes a lot of bus
bandwidth. The signatures are not guaranteed to be unique
across different operating systems, potentially leading
to data corruption.
The Access Controls proposal introduces the concept of a
central management agent (PAM) that controls policies
working with targets that implement those policies.
Something like this could be useful for the boot problem.
Each target could maintain a list (similar to the access
control list) indicating which initiators the management
agent has decreed are allowed to/should search for boot
devices on that target. The management agent would
be responsible for configuring the lists. The target
would return an indication of whether the "bootable"
bit is set for the initiator making that inquiry.
I imagine there are other attributes other than "bootable"
that might be useful too.
Is there any interest in something like this?
Rob Elliott UNIX mailto:relliott at hobbit.eng.hou.compaq.com
Houston, TX PC mailto:Robert.Elliott at compaq.com
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