Library Partitioning - Dell EMC ML3 User Manual

Multiple control paths reduce the possibility of a failure in one control path to cause the entire library to
become unavailable. Also, when you configure more control paths, more library-sharing configurations
and options are possible. Access to the library is on a first-come, first-served basis. Each control path for a
logical library can accept commands while the library is in use by another control path.
Multiple control paths for control path failover
This tape library offers an optional control path failover feature. See "Library sharing" on page 17 and
"Path failover and load balancing" on page 18.
Use of the control path failover feature further reduces the possibility of a failure in one control path to
cause the entire library to become unavailable.
The control path failover feature (feature code 1682) enables the host device driver to resend a command
to a different control path for the same logical library.

Library partitioning

Libraries that contain at least two drives can configure two logical libraries. It is possible to configure up
to 21 logical libraries in the library (up to the number of drives installed). In a partitioned library, the
Operator Panel reports only the status of logical library 1 in the main menu because of space limitations.
The user must go to the logical libraries status in the Operator Panel to get the information about the
additional library partitions. The Management GUI provides a Logical Library Graphical View.
Partitioning of libraries
With full-height or half-height physical drives, physical numbering is bottom up for all drives. For
example, if you replace a half-height drive in Figure 22 on page 16, the drives are still numbered 1-4. If
you add a drive in any of the slots in between drives numbered 1 and 4, the physical numbering changes
and is still numbered bottom up.
Important: A full-height drive can be installed in a module in the lower two slots only.
Configuration of a 1-logical library system
A one logical library system contains all drives present in any drive positions, and it contains all the slots.
Configuration of multiple logical libraries
A library with multiple logical libraries must have a drive for each logical library and at least one slot.
Drives can be in any location in the library. It is best to have drives that are located near the slots that are
assigned to the same logical library to minimize accessor movement and maximize performance.
SCSI element-addressing
A logical library assigns SCSI element addresses to drives, storage slots, I/O slots, and the accessor. For
each element type (drive, storage, I/O), the SCSI element address can be viewed on the Management
GUI.
While SCSI addressing follows the same method as physical location-numbering, this action depends on
the Advanced Logical Library configuration.
Drive numbering is from bottom to top. Storage slot-numbering is from left magazine (front to back,
bottom to top) to right magazine (back to front, bottom to top). IO slot-numbering is from bottom to top.
Accessor is single number.
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