Restrictions and Limitations when configuring mixed LTO tapes in TSM


Tivoli Storage Manager also supports the tape library which has mixed LTO generations besides traditional tape libraries with same device type drives. However, the mixing of different generations of the same type of drive is still not supported. New drives cannot write the older media formats, and old drives cannot read new formats. 

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When mixing different generations of LTO drives and media, you need to consider the read-write capabilities of each generation. As a best practice, configure a different device class for each generation of media. If you are considering mixing different generations of LTO media and drives in your TSM environment , be aware of the following restrictions.
  • If you are mixing different types of drives and media, configure different device classes, one for each type of media. To specify the exact media type, use the FORMAT parameter in each of the device class definitions. (Do not specify FORMAT=DRIVE). 
  • For example, if you are mixing Ultrium Generation 1 and Ultrium Generation 2 drives, specify FORMAT=ULTRIUMC (or ULTRIUM) for the Ultrium Generation 1 device class, and FORMAT=ULTRIUM2C (or ULTRIUM2) for the Ultrium Generation 2 device class.
          define devclass LTO1 library=TSMLIB devtype=LTO format=ULTRIUM
          define devclass LTO2C library=TSMLIB devtype=LTO format=ULTRIUM2C

            here C is referred for Compression
  • Both device classes can point to the same library in which there can be Ultrium Generation 1 and Ultrium Generation 2 drives. The drives will be shared between the two storage pools. One storage pool will use the first device class and Ultrium Generation 1 media exclusively. The other storage pool will use the second device class and Ultrium Generation 2 media exclusively. Because the two storage pools share a single library, Ultrium Generation 1 media can be mounted on Ultrium Generation 2 drives as they become available during mount point processing.
          define stgpool LTOpool LTO1
          define stgpool LTO2pool LTO2C

There are also exceptions to the rule against mixing generations of LTO Ultrium drives and media. The Tivoli Storage Manager server support mixtures of the following types
  • LTO Ultrium Generation 1 (LTO1) and LTO Ultrium Generation 2 (LTO2)
  • LTO Ultrium Generation 2 (LTO2) with LTO Ultrium Generation 3 (LTO3)
  • LTO Ultrium Generation 3 (LTO3) with LTO Ultrium Generation 4 (LTO4)
  • LTO Ultrium Generation 4 (LTO4) with LTO Ultrium Generation 5 (LTO5)
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LTO Ultrium Generations Specifications

Generation 1
First licensed in 1998, with product appearing in 2000, Ultrium format Generation 1 provides cartridge capacities of up to 200 GB (2:1 compression) and up to 100 GB native with data transfer rates of up to 40 MB/ second (2:1 compression).

Generation 2
With a cartridge capacity of up to 400 GB (2:1 compression) and up to 200 GB native, Ultrium format Generation 2 provides data transfer rates of up to 80 MB/second (2:1 compression). Licenses for Generation 2 became available in April 2002 with products appearing in late 2002.

Generation 3
Featuring capacities of 800 GB (2:1 compression) and up to 400 GB native per cartridge, Ultrium format Generation 3 provides data transfer rates of up to 160 MB/second (2:1 compression) for the third generation of the 8-channel version. Generation 3 licenses became available on July 26, 2004 with products appearing in late 2004.

Generation 4
Delivering 1.6TB (2:1 compression) and up to 800 GB native per cartridge, Ultrium format Generation 4 provides data transfer rates of up to 240 MB/second (2:1 compression), the LTO Ultrium format generation specification was made available to licensees in late December 2006.

Generation 5
Delivering 3 TB (assuming a 2:1 compression), up to 280 MB/s (assuming a 2:1 compression), and adds a new partitioning feature and Linerar Tape File System specification to provide enhanced file control and data management. The LTO Ultrium format generation 5 specifications were made available to licensees in January 2010.

Generation 6
With capacity of 6.25 TB (assuming a 2.5:1 compression), LTO Ultrium generation 6 provides data transfer speeds of up to 400 MB/s (assuming a 2.5:1 compression) and continues support of partitioning to enable functions like LTFS making tape easy to manage, encryption - helping to secure data, and WORM to address compliance needs.


Future LTO Ultrium Generations

Generation 7
Capacity: Up to 16 TB (assuming a 2.5:1 compression)
Data transfer speed: up to 788 MB/s (assuming a 2.5:1 compression)

Generation 8
Capacity: Up to 32 TB (assuming a 2.5:1 compression)
Data transfer speed: up to 1,180 MB/s (assuming a 2.5:1 compression)

LTO Ultrium tape drives Limitations

  • LTO Ultrium Generation 3 drives can only read Generation 1 media. If you are mixing Ultrium Generation 1 with Ultrium Generation 3 drives and media in a single library, you must mark the Generation 1 media as read-only, and all Generation 1 scratch volumes must be checked out.
  • LTO Ultrium Generation 4 drives can only read Generation 2 media. If you are mixing Ultrium Generation 2 with Ultrium Generation 4 drives and media in a single library, you must mark the Generation 2 media as read-only, and all Generation 2 scratch volumes must be checked out.
  • LTO Ultrium Generation 5 drives can only read Generation 3 media. If you are mixing Ultrium Generation 3 with Ultrium Generation 5 drives and media in a single library, you must mark the Generation 3 media as read-only, and all Generation 3 scratch volumes must be checked out.
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Importance of MOUNTLIMIT parameter in mixed device class definitions

If your TSM environment has a mixed LTO device type drives then you should carefully decide the value for the MOUNTLIMIT parameter while defining device classes for these device types. For example in a mixed media library containing Ultrium Generation 1 and Ultrium Generation 2 drives and media, Ultrium Generation 1 media can get mounted in Ultrium Generation 2 drives.



Consider the example of a mixed library that consists of the following drives and media

  • Four LTO Ultrium Generation 1 drives and LTO Ultrium Generation 1 media
  • Four LTO Ultrium Generation 2 drives and LTO Ultrium Generation 2 media
You created the following device classes

LTO Ultrium Generation 1 device class LTO1CLASS specifying FORMAT=ULTRIUMC

LTO Ultrium Generation 2 device class LTO2CLASS specifying FORMAT=ULTRIUM2C


You also created the following storage pools

LTO Ultrium Generation 1 storage pool LTO1POOL based on device class LTO1CLASS
 LTO Ultrium Generation 2 storage pool LTO2POOL based on device classLTO2CLASS

The number of mount points available for use by each storage pool is specified in the device class using the MOUNTLIMIT parameter. 
  • The MOUNTLIMIT parameter in the LTO2CLASS device class should be set to 4 to match the number of available drives that can mount only LTO2 media. 
  • The MOUNTLIMIT parameter in the LTO1CLASS device class should be set to a value higher (5 or possibly 6) than the number of available drives to adjust for the fact that Ultrium Generation 1 media can be mounted in Ultrium Generation 2 drives. 
  • The optimum value for MOUNTLIMIT will depend on workload and storage pool access patterns. 
Monitor and adjust the MOUNTLIMIT setting to suit changing workloads. If the MOUNTLIMIT for LTO1POOL is set too high, mount requests for the LTO2POOL might be delayed or fail because the Ultrium Generation 2 drives have been used to satisfy Ultrium Generation 1 mount requests. In the worst scenario, too much competition for Ultrium Generation 2 drives might cause mounts for Generation 2 media to fail with the following message:

ANR8447E No drives are currently available in the library.

If the MOUNTLIMIT for LTO1POOL is not set high enough, mount requests that could potentially be satisfied LTO Ultrium Generation 2 drives will be delayed. 

Some restrictions apply when mixing Ultrium Generation 1 with Ultrium Generation 2 or Generation 3 drives because of the way in which mount points are allocated. For example, processes that require multiple mount points (MOVE DATA & BACKUP STGPOOL) that include both Ultrium Generation 1 and Ultrium Generation 2 volumes might try to reserve Ultrium Generation 2 drives only, even when one mount can be satisfied by an available Ultrium Generation 1 drive. These processes will wait until the needed number of mount points can be satisfied with Ultrium Generation 2 drives.




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