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@overlandstorage.com
"Rose, Roger"
<Rrose@tandbergdata.com>
12/19/2007 02:21 PM
To
<GBarton@overlandstorage.com>,
<t10@t10.org>
cc
Subject
RE: ADI - SMC tape alerts using ADI
bridging (re proposal 06-420r2 and smc3r09)
This is currently covered by ADC
section 4.2.6 and ADC-2 Rev 8 section 4.6.
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@t10.org [mailto:owner-t10@t10.org]
On Behalf Of GBarton@overlandstorage.com
Sent: Tuesday, December 18, 2007 3:07 PM
To: curtis.ballard@hp.com; michael_banther@hp.com; kdbutt@us.ibm.com;
halvard.eriksen@tandbergstorage.com; PayneR@iomega.com; Paul.Stone@Quantum.com;
paul.suhler@Quantum.com
Cc: t10@t10.org
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
exists.
regards,
Geoffrey L. Barton
Overland Storage
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