ADI - SMC tape alerts using ADI bridging (re proposal 06-420r2 and smc3r09)

GBarton at GBarton at
Tue Dec 18 14:06:41 PST 2007

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In reviewing Michael Banther's proposal for tape alert flag (06-420r2), it 
occurred to me that there is a problem with SMC tape alerts in general if 
ADI bridging is being used for host access to the library. 
smc3r09 clause 5.2.2 third paragraph defines deactivations for tape 
alerts. Numbered list 1) states "after the TapeAlert log page is read. The 
TapeAlert flags shall be deactivated on a per-initiator basis such that 
active flags are available for other initiators; ". 
and in proposal 06-420r2 clause 5.4.4 last paragraph, the same statement 
is made with "should" instead of "shall".
Since a library device using ADI bridging is not aware of initiators, the 
library cannot clear the flags on a per initiator basis. Does this mean 
the DT device must cache the tape alert log page and keep track of the 
reads of that log page? If so, how does the DT device know when to cache a 
new page? And if the DT device handles the tape alert log page on a per 
initiator basis, how does the library know when to clear the flags? As far 
as I can tell, there is no mechanism to handle this.
Even if proposal 06-420r2 is not incorporated into smc3, the problem still 
Geoffrey L. Barton
Overland Storage
Tiered Data Protection Made Simple

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