Disabling reserve release is important in an SSO environment, as the media
server sends a

mt -f <dev file> rewoffl

to eject the tape after job completion.

Ayaz
#!/a.k.a/jazz
_____________________________________________________________
Ayaz Mudarris, Senior Consultant
Collective                      http://www.collectivetech.com
Tel  (312) 781-6200             eFax (253) 541-2141

> -----Original Message-----
> From: veritas-bu-admin AT mailman.eng.auburn DOT edu
> [mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Marelas,
> Peter
> Sent: Monday, April 16, 2001 10:33 AM
> To: 'Jason Ahrens [ahrensj AT psi DOT ca]'
> Cc: 'veritas-bu AT mailman.eng.auburn DOT edu'
> Subject: RE: [Veritas-bu] SCSI Reserve/Release
>
>
> 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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