HP 12000 HP 12200 Gateway Virtual Library System User Guide (BW403-10001, June - Page 90

Managing Virtual Device LUNs, Default LUN Numbering

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of the additional storage you make available by erasing cartridges. First erase cartridges from your backup application, then follow the procedure below. From Command View VLS: 1. On the System tab, select Chassis from the navigation screen to open the Chassis status screen. 2. Select Reclaim Space in the task bar. The VLS system initiates space reclamation and the Notifications screen displays a notification of the scheduled reclamation. Managing Virtual Device LUNs The VLS has a LUN masking, a LUN mapping, and a port mapping feature that allows you to restrict host access to the LUNs (virtual libraries and tape drives) configured on the VLS and assign each virtual device to a specific Fibre Channel host port. These features allow you to allocate the virtual devices to individual hosts and distribute the virtual tape drives across the Fibre Channel host ports to achieve maximum bandwidth. See "Managing high availability" (page 103) for more information. You can set a global default so that either the VLS allows all hosts connected to the VLS through the SAN to access all virtual devices configured on the VLS, or the VLS prevents all hosts from viewing any virtual devices until they are explicitly mapped to the host. Each time you add a new host to the VLS, it takes the global default you have set. The VLS firmware also manages the LUN numbering so that the virtual device LUN assignments always meet operating system requirements and restrictions. See "Default LUN Numbering" (page 90) and "Operating System LUN Requirements and Restrictions" (page 90). Port mapping is required and allows you to assign each virtual device to one of the Fibre Channel host ports or a pair of Fibre Channel host ports (if your backup solution supports this). Default LUN Numbering The VLS automatically assigns a logical unit number (LUN) to each virtual library and tape drive created on the VLS in the order in which they are created by you, starting with LUN0 and increasing incrementally by one as each new virtual library or tape drive is created on an Fibre Channel host port (LUN1, LUN2, and so on). The first virtual device port mapped to any of the Fibre Channel host ports is assigned the LUN number LUN0. The second virtual device port mapped to an Fibre Channel host port is assigned the LUN number LUN1, and so on. The default LUN numbers are changed by the VLS firmware when the VLS device emulations are restarted if: • A virtual device has been deleted since the last restart, creating a gap in the LUN numbering, or • A virtual tape drive has been added to a library since the last restart and the default LUN number it was assigned is not consecutive with the other virtual tape drives in the same library. Restarting VLS device emulations changes the default LUN numbers as necessary to remove the gap or to make the virtual tape drive LUN numbers consecutive in each library. This is done so that the virtual device LUN numbering meets the operating system LUN requirements. NOTE: When a LUN has been unconfigured or otherwise deleted, it may still show up in the VLS user interface. Use the VLS discovery utility to refresh the list of LUNs that are present. Operating System LUN Requirements and Restrictions Most operating systems require that each VLS Fibre Channel host port connected to the SAN has a virtual device with the LUN number LUN0 and no gaps in the LUN numbering (LUN0, LUN1, LUN2, and so on). If the operating system does not see a LUN0 on a VLS Fibre Channel host port when it is scanning for new hardware on the SAN, it will stop looking for LUNs on that port and 90 Configuration

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of the additional storage you make available by erasing cartridges. First erase cartridges from
your backup application, then follow the procedure below.
From Command View VLS:
1.
On the
System
tab, select
Chassis
from the navigation screen to open the Chassis status screen.
2.
Select
Reclaim Space
in the task bar.
The VLS system initiates space reclamation and the Notifications screen displays a notification
of the scheduled reclamation.
Managing Virtual Device LUNs
The VLS has a LUN masking, a LUN mapping, and a port mapping feature that allows you to
restrict host access to the LUNs (virtual libraries and tape drives) configured on the VLS and assign
each virtual device to a specific Fibre Channel host port. These features allow you to allocate the
virtual devices to individual hosts and distribute the virtual tape drives across the Fibre Channel
host ports to achieve maximum bandwidth. See
“Managing high availability” (page 103)
for more
information.
You can set a global default so that either the VLS allows all hosts connected to the VLS through
the SAN to access all virtual devices configured on the VLS, or the VLS prevents all hosts from
viewing any virtual devices until they are explicitly mapped to the host. Each time you add a new
host to the VLS, it takes the global default you have set. The VLS firmware also manages the LUN
numbering so that the virtual device LUN assignments always meet operating system requirements
and restrictions. See
“Default LUN Numbering” (page 90)
and
“Operating System LUN Requirements
and Restrictions” (page 90)
.
Port mapping is required and allows you to assign each virtual device to one of the Fibre Channel
host ports or a pair of Fibre Channel host ports (if your backup solution supports this).
Default LUN Numbering
The VLS automatically assigns a logical unit number (LUN) to each virtual library and tape drive
created on the VLS in the order in which they are created by you, starting with LUN0 and increasing
incrementally by one as each new virtual library or tape drive is created on an Fibre Channel host
port (LUN1, LUN2, and so on). The first virtual device port mapped to any of the Fibre Channel
host ports is assigned the LUN number LUN0. The second virtual device port mapped to an Fibre
Channel host port is assigned the LUN number LUN1, and so on.
The default LUN numbers are changed by the VLS firmware when the VLS device emulations are
restarted if:
•
A virtual device has been deleted since the last restart, creating a gap in the LUN numbering,
or
•
A virtual tape drive has been added to a library since the last restart and the default LUN
number it was assigned is not consecutive with the other virtual tape drives in the same library.
Restarting VLS device emulations changes the default LUN numbers as necessary to remove the
gap or to make the virtual tape drive LUN numbers consecutive in each library. This is done so
that the virtual device LUN numbering meets the operating system LUN requirements.
NOTE:
When a LUN has been unconfigured or otherwise deleted, it may still show up in the VLS
user interface. Use the VLS discovery utility to refresh the list of LUNs that are present.
Operating System LUN Requirements and Restrictions
Most operating systems require that each VLS Fibre Channel host port connected to the SAN has
a virtual device with the LUN number LUN0 and no gaps in the LUN numbering (LUN0, LUN1,
LUN2, and so on). If the operating system does not see a LUN0 on a VLS Fibre Channel host port
when it is scanning for new hardware on the SAN, it will stop looking for LUNs on that port and
90
Configuration