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DPTIPS: Busy Drive Handling Made Easy

The robotic arm in your tape library is responsible for maintaining a map of where all of its media is located.  It knows what tapes reside in storage slots, mail slots, the arm's gripper, and each tape drive.  For the media that is mounted in a drive, the arm also knows the storage slot from which it came.  It's true for physical tape libraries like HP's ESL, EML, and MSL products as well as appliances that emulate tape libraries like HP's D2D StoreOnce and Virtual Library Systems.

 

Consider the default behavior enumerated in this example:

 

  1. A new backup starts after recovering from a crash of your Cell Manager machine.
  2. The Backup Media Agent (BMA) tells the Utility Media Agent (UMA) to fetch a tape from storage slot 10 and mount it in drive 2.
  3. The robotic arm informs UMA that it cannot satisfy the tape mount because drive 2 already has a tape in it.
  4. The session aborts.

So what?  So what if I told you that one simple change in your Data Protector library properties can leverage the robot's inventory information to no longer abort backup sessions when UMA unexpectedly encounters a tape left behind in a tape drive that it wishes to load with a new tape.

 

Using your context drop-down, select Devices & Media.

 

Scoping Pane - Devices & Media

 

In the scoping pane (left side) with your environment tree, expand Devices, right-click your library, and select Properties ...

 

Library Properties

 

Here's where we get down to business.  In the results pane (right side), select the Control tab.  Look for the Busy drive handling section.  Note that the default is Abort.  Using the drop-down menu, change the parameter from Abort to Eject medium.

 

Eject Medium vs. Abort

 

Don't forget to apply your changes!

 

With our new setting for busy drive handling, let's revisit the train wreck in my previous example.  What will be different this time?

 

  1. A new backup starts after recovering from a crash of your Cell Manager machine.
  2. The Backup Media Agent (BMA) tells the Utility Media Agent (UMA) to fetch a tape from storage slot 10 and mount it in drive 2.
  3. The robotic arm informs UMA that it cannot satisfy the tape mount because drive 2 already has a tape in it.
  4. UMA instructs the robot to dismount the tape in drive 2 and return it to the storage slot from whence it came.
  5. UMA then queues a command to mount the tape from storage slot 10 in the freshly-emptied drive 2.
  6. The tape load succeeds, and your backup proceeds as usual.

Your backup completes successfully, your slumber is uninterrupted by a call from tech support, and you are once again the hero of enterprise backup and recovery -- a giant among your peers.  The only thing missing is a cape!  (And the ability to fly.)

Labels: Data Protector
Comments
Technical Support Services | ‎12-01-2011 10:40 AM

A nice blog to handle technical errors related to bus drive and made it easy.

ChadV | ‎12-01-2011 02:46 PM

If the device is already in use, by an already running job, will the newly started session interrupt the one that is running or will it queue up and wait for it to finish? Just wanted to make sure that this did not give it the liberty to interrupt already running backups.

Mr_T | ‎12-08-2011 02:43 AM

Devices locked by currently running backups will not be interrupted.  Only if a tape is encountered in an unlocked drive will the unload take place.

Computer support Birmingham | ‎08-23-2012 01:03 PM

Really nice solution...I was facing this king of problem.. thanks for solution...

Jasvir Singh | ‎10-19-2012 09:10 AM

What if already a Backup is running on that drive. And another session starts. Then what is the change we have to do, that The next session wait for the drive to free and not abort the session at a time..???

Mr_T | ‎10-19-2012 01:34 PM

Hello Jasvir,

 

If another Data Protector backup is running, then Data Protector knows the drive is locked (in use) and will not attempt to use it for a new backup until it is free.  In that case, yes, the new job will queue pending availability of a free drive and will not interrupt the running backup.

 

You can check on which drives, cartridges, and slots are locked at any given time by running the command "omnimm -show_locked_devs".  Here is sample output from my cell manager with no sessions running:

 

C:\Users\Administrator>omnimm -show_locked_devs
No locked devices/media/cartridges found!

Busy drive handling becomes relevant when Data Protector encounters an occupied drive that it didn't know about.  That can happen after a cell manager crash/reboot if backups were previously in progress.  State information for drives and media are not retained after a reboot.  Data Protector will have no locked devices after a cell manager reboot which means it will have lost track of what was in progress before the boot and which drives/cartridges were in use.  That's when you want the library robot to put the orphaned cartridge back where it came from and not simply abort the device in a new backup when an occupied drive is encountered.

 

Thank you for your question, and have a wonderful day!

 

-- Mr_T

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Mr_T? Yes, but in name only. No mohawk or gold chains. In real life I'm Jim Turner, a Master Technologist with HP's Integration and Techn...
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