Ravi,

Is that a solaris setting? If so, no I havent.
We disable sending target resets in the JNI HBA driver.
Hopefully once we sort out the issues were dealing with
I can relay my experiences.

Regards
Peter Marelas

-----Original Message-----
From: Ravi Channavajhala [mailto:ravi.channavajhala AT csfb DOT com]
Sent: Tuesday, 17 April 2001 6:32 AM
To: Marelas, Peter
Cc: 'veritas-bu AT mailman.eng.auburn DOT edu'
Subject: RE: [Veritas-bu] SCSI Reserve/Release


Peter,

Just for my info, have you played with scsi_reset_delay value?
As for the rest of your mail, I'm on the verge of pilotting
backups in SAN, and I cant agree more that there is no way
to control the usage of 'mt', 'tar' etc., Hopefully, I can
find all the related problems during my SAN backup pilot.

-ravi

On Tue, 17 Apr 2001, Marelas, Peter wrote:

>Im sending the response to the list as Im getting queries about what
>exactly SCSI reserve/release is.
>
>The SCSI protocol has a feature to arbitrate access to a device at
>the SCSI level. It does so using SCSI reservations. When a device
>wants to open a SCSI device it first attempts to obtain a reservation.
>If the device is in use, the attempt will fail with busy. The host may
>however
>force a reservation by sending a target reset, causing the device to
>release its reserve, and allowing the host to attempt another reserve.
>The reset is "last resort" tactics. Bearing in mind, some tape drives
>rewind on reset.
>
>The setting is discussed lightly in 3.4 manuals for Solaris. I dont see a
>mention
>for other platforms media servers. In particular it talks about disabling
>reserve/release in st.conf. It also refers to an old version of Solaris 2.5
>and
>an st patch.
>
>We are currently running without reserve/release and have experienced
>arbitration issues. We have seen media been overwritten and corrupt
>media labels. We have seen media servers not agreeing as to what each
>drive is up to or what tape is in the drives.
>
>Based on our own analysis It seems if you disable reserve/release, only SSO
>is in
>control of arbitration to drives. However, SSO does not seem to arbitrate
>access
>to devices outside of netbackups command set, thus a tar, mt, dd against
rmt
>devices will cause unpredictable results.
>
>Its unclear then, from the manuals, whether disabling SCSI reserve/release
>is
>really what we should be doing. Given, in a large scale SAN environment
with
>many media servers, its very difficult to tell whos doing what to the tape
>drives
>via Solaris command set. In addition, SAN is hetrogeneous. Do we disable
>reserve/release in NT/AIX/True64? Theres no mention of this anywhere.
>
>Thats what prompted the original email. Ive discussed the issue with
Veritas
>to death. Th responses I get are inconsistent depending on who you talk to.
>I wanted to hear from real life examples.
>
>Regards
>Peter Marelas
>
>
>
>> -----Original Message-----
>> From:        Jason Ahrens [ahrensj AT psi DOT ca] [SMTP:AhrensJ AT psi DOT 
>> ca]
>> Sent:        Tuesday, 17 April 2001 1:07 AM
>> To:  Veritas BU
>> Subject:     RE: [Veritas-bu] SCSI Reserve/Release
>> 
>> Out of curiosity (as I am using these same drives) what is this
>> Reserve/Release?
>> 
>> Jason
>> 
>> -----Original Message-----
>> From: Marelas, Peter [mailto:MarelP AT AUSTRALIA.Stortek DOT com]
>> Sent: April 16, 2001 08:00
>> To: 'veritas-bu AT mailman.eng.auburn DOT edu'
>> Subject: [Veritas-bu] SCSI Reserve/Release
>> 
>> 
>> Hi,
>> 
>> I'ld like to take a poll on how many installations of Netbackup 3.2GA or
>> 3.4
>> in a Fabric Switched SAN environment
>> with Shared Storage Option, have enabled SCSI Reserve/Release in the
>> Solaris
>> st driver (st.conf).
>> 
>> Please let me know if you have a similar environment and whether you
>> enabled
>> reserve/release.
>> Also, I would be interested to hear of any problems experienced if
>> reserve/release is NOT enabled, and if
>> reserve/release IS enabled.
>> 
>> Peter Marelas
>> Senior Consultant
>> 0410 497 228 Mobile
>> 61.3.9699.1033 Phone
>> 61.3.9690.8528 Fax
>> StorageTek
>> INFORMATION made POWERFUL
>> 
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