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

GBarton at GBarton at
Wed Dec 19 14:56:35 PST 2007

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I think what you are talking about is the TapeAlert for the DT device 
(tape drive) as specified in ssc2 that the library can use to track and/or 
report problems in it's tape drives. I am talking about the library 
TapAlerts defined in smc2 and currently smc3 and referred to in proposal 
06-420r2. Currently, log page 12h TapeAlert Response Log Page is not 
currently specified in smc2 or smc3. Rather, log page 2Eh TapeAlert Log 
Page. If the host access to the library is through the ADI bridge, the 
host (or hosts) can request log page 2Eh. There is currently no mechanism 
using ADI bridging to clear the flags at the library on a per I-T nexus 
basis, since the library has no visibility of the initiator. The DT device 
(tape drive) can keep track of which initiators have requested page 2Eh, 
but there is no mechanism to keep the tape drive up to date on current 
tape alerts set, unless the DT device passes the log sense command through 
the bridge (which will clear the flags in the library) and intercepts the 
log page and updates cached values accordingly. Is this being done by tape 
drives? I have not run an experiment to find out.
Geoffrey L. Barton
Overland Storage
4820 Overland Ave.
San Diego, CA 92123
858 974-4586
gbarton at
"Rose, Roger" <Rrose at> 
12/19/2007 02:21 PM
<GBarton at>, <t10 at>
RE: ADI - SMC tape alerts using ADI bridging (re proposal 06-420r2 and 
This is currently covered by ADC section 4.2.6 and ADC-2 Rev 8 section 
>From ADC-2:
4.6 TapeAlert application client interface
The ADC device server supports a modified version of TapeAlert specified 
in SSC-2. As supported by the ADC device server, the TapeAlert flags 
represent states, and the state flags are not set to zero upon retrieval 
of the TapeAlert Response log page (see 6.1.3). Instead, the state flags 
are set to zero upon a change of the condition involved with the state 
(see table 5).
-roger rose
 Product Test, Tandberg Data
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of 
GBarton at
Sent: Tuesday, December 18, 2007 3:07 PM
To: curtis.ballard at; michael_banther at; kdbutt at; 
halvard.eriksen at; PayneR at; 
Paul.Stone at; paul.suhler at
Cc: t10 at
Subject: ADI - SMC tape alerts using ADI bridging (re proposal 06-420r2 
and smc3r09)
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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