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tape library partitioning

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penta
Occasional Contributor

tape library partitioning

Assume a tape library partitioned into two logical libraries.
Can a host access more than one logical library in a partitioned library?

If it can, how does a backup application differentiate between the two logical libraries ?

Would the device identifiers/serial number returned for an SCSI INQUIRY command be different for the associated medium changer devices ?

Thanks,
penta
7 REPLIES
Torsten.
Acclaimed Contributor

Re: tape library partitioning

Hi,

for this question:

"Can a host access more than one logical library in a partitioned library?"

Why do you want to do this?
I cannot imagine any sense...

Hope this helps!
Regards
Torsten.

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Rob Leadbeater
Honored Contributor

Re: tape library partitioning

Hi,

I'm with Torsten on this one, although I got stuck on the fist line...

"Assume a tape library partitioned into two logical libraries."

A tape library will have a defined number of drives and slots at the SCSI level. I can't think of any easy way how that could be split into two logical libraries.

Perhaps if you explained exactly what you're trying to achieve it might make more sense...

Cheers,

Rob
Torsten.
Acclaimed Contributor

Re: tape library partitioning

Rob, the EML and eESL libs are able to split and I guess the virtual lib's can simulate anything ... but the question about the reason remains ...

Hope this helps!
Regards
Torsten.

__________________________________________________
There are only 10 types of people in the world -
those who understand binary, and those who don't.

__________________________________________________
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penta
Occasional Contributor

Re: tape library partitioning


Suppose the physical tape library has 2 drives and 40 slots and its partitioned into two, giving each partition 1 drive and 20 slots. If the 2 drives are of different types for mixed media support you could do hardware partitioning of the tape library and each partition would cater to a different media type.

My interest is more from a backup application point of view. How do i differentiate in a program between the two partitions assuming that the server can access both.

For example in a program i would
1. Send SCSI inquiry to each medium changer device, and based on the the device identification, serial numbers etc
2. For each different medium changer device detected, i would perform its inventory based by reading element status etc..

SCSI INQUIRY VPD page 0x83(device identification) and 0x80(serial number) output helps me distinguish between different medium changer devices.
In the case of the library partitions in the above would the output for the VPD pages be different or would it have been the same as that returned for the unpartitioned library

Thanks,
penta
whiz_kid
Regular Advisor
Solution

Re: tape library partitioning

i believe a host can access more than one logical library from a partitioned libaray. and i guess the backup software would see it as two different libraries. The SCSI INQUIRY would list two different serial numbers for medium changers.


Curtis Ballard
Honored Contributor

Re: tape library partitioning

The post by whiz kid is correct. When you partition a library the partitioning software will generate new serial numbers and world wide names so that from an application view there are multiple libraries available.

Note that because the serial numbers have to be generated for each partition the serial number you ISV application lists for the library will no longer match the hardware serial number on the library. If you call tech support they will be able to recognize partitioned library serial numbers and point you to the hardware serial number.
penta
Occasional Contributor

Re: tape library partitioning

Thanks! I understand now.