Re: Towards Consensus on TCP Connections

[csapuntz@cisco.com]

Black_David@emc.com writes:

> > There are two ways in which multiple connections are used in iSCSI:
> > 
> > 1) Multiple simultaneous TCP connections for bandwidth
> > 	
> > 2) Multiple TCP connections for fault tolerance/recovery
> > 	(i.e. when one TCP connection in a session dies, 
> >          another one starts up)
> 
> It is an established practice in the storage industry
> to achieve both 1) and 2) via the use of multiple
> SCSI connections, and evidenced by numerous products
> that do this for host access to storage.  Hence a
> "no" answer to (B) does not preclude the use of
> multiple TCP connections for bandwidth or fault
> tolerance/recovery as long as one is willing to use
> multiple SCSI connections to do so.

On recovery, a big concern was the tape backup issue. Do SCSI
applications recover gracefully today from failed SCSI connections?
My understanding was that many tape backups program abort the backup.

Related to recovery, when a TCP/SCSI connection closes, what ramifications
does it have on device state (like mode pages, PREVENT/ALLOW REMOVAL,
RESERVE/RELEASE, etc.)? Where does SCSI specify this?

Thanks,
-Costa