Re: iSCSI: login issue - partial consensus call

[Santosh Rao <santoshr@cup.hp.com>]

"Martin, Nick" wrote:

> The problem is that iSCSI does not and will not specify how two HBAs
> from different vendors installed in the same Initiator should or could
> get a range of ISIDs for their exclusive use.  This will be operating
> system specific and vendor defined.  It is uncertain that the same tool
> or repository would be used by all HBA vendors in any environment.
> Given this, accidental overlap in ISID space is not unlikely.

In the above scenario, if the HBAs do not have an interface to receive a
range of ISIDs from the OS iscsi driver, then, they must also lack an
interface to be handed down an iscsi initiator node name from the
OS driver. Without using a common iscsi initiator node name, the ISID issue
does not arise for multiple HBAs. [since each would be using its own iscsi
name].

OTOH, if the HBAs have an interface to be handed down an iscsi initiator
node name from the OS driver, there's no reason for them to not provide an
interface to be handed down an ISID or a range of ISIDs for their use.

I am in favor of option (A) since it is the simplest and a well designed
HBA should be providing interfaces for the OS driver to assign the HBA an
iscsi initiator node name as well as a range of ISIDs, thus, rendering
Nick's scenario unlikely.

>
> Given that there is no one way to play right, we must make sure that
> everyone can at least play nice.
>
> My expectation is that sessions are infrequently established and long
> lived.  ISIDs may be re-used at will by their current owners.  When no
> "already owned" ISIDs are available, or an attempt to re-use an "already
> owned" ISID failed, and HBA would need to a) "probe" for a new available
> ISID or b) fail the request to establish the session.  Session recovery
> should not be attempted unless a session is known to have failed.
>
> If tools are available, and the administrator has used them correctly,
> then HBAs will not collide in ISID space.  If the tools are not
> available or were not used correctly, I would hope the second HBA can
> still attempt to come up without impacting the sessions established by
> the first.

If the tools were not available, how does the 2nd HBA get assigned the same
iscsi initiator node name as the first ? The ISID issue is only applicable
if both HBAs are sharing the same iscsi initiator node name.

I would like to understand the rationale behind an HBA interface allowing
an initiator node name to be assigned, but not an ISID or a range of ISIDs
(?).


Regards,
Santosh


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