Re: iSCSI: multiple intiaitor conflicting with target (was Re: iSCSI:response to second login (with same ISID)

[Patrick Stirling <pms@veritas.com>]

On Tue, 29 May 2001, Sanjeev Bhagat (TRIPACE/Zoetermeer) wrote:

> Since the initiators are two different entities working completely
> independent of each other they cannot co-ordinate with each other. iSCSI
> Target also sees these two different initiators in different sessions as
> seperate entities. In the current implementation of iSCSI I guess it is not
> possible for two different initiators to know about each other and so it is
> difficult to resolve this conflicting situation.
> 
> The answer to this problem might be lying in SAM-2 specifications. May be I
> am missing something there. Can somebody comment?

As far as I'm aware, you have two options:

- the initiators co-operate to share the device
- the initiators make reservations to lock each other out (in which case
  one could assert that they have indirect knowledge of each other)

BTW this is a general SCSI issue, not confined to iSCSI. Note that you
must also be careful about target resets & other task management commands
here. Also note that when devices are shared it's usually done above the
initiator level, i.e. there's an application using the initiator to access
the device, and it's aware of other initiators. One might say "it's a
layering issue" - SCSI provides reservations to help share devices, but
it's up to higher layers to coordinate the sharing.

patrick