IBM System Storage TS3500, Введение и руководство по планированию

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Attention: The HD slots have a constant force spring for maintaining forward
pressure on the tape cartridges. Use caution when inserting or removing cartridges
from HD slots.
HD frame model S24 provides storage for up to 1 000 IBM 3592 tape cartridges.
HD frame model S54 provides storage for up to 1 320 LTO Ultrium tape cartridges.
The base capacity of Model S24 is 600 cartridges, which are stored in Tiers 0, 1,
and 2. The base capacity of Model S54 is 660 cartridges, which are stored in Tiers
0, 1, and 2. In order to increase capacity to the maximum for each frame, it is
necessary to purchase the High Density Capacity on Demand (HD CoD) feature.
This feature provides a license key that enables you to utilize the storage space
available in the remaining tiers. For more information, see “High Density Capacity
On Demand” on page 55.
Note: These numbers represent raw capacity and do not reflect actual
recommended capacity. It is recommended that actual capacity does not exceed
99% of the raw capacity due to the need to maintain unused slots in order to
perform a
shuffle operation.
In HD frames, the cartridge accessor performs a shuffle operation in order to access
the cartridges stored in Tier 2 and beyond. A shuffle is the process of moving
cartridges in lower tiers into the gripper, or other available slots, in order to access
cartridges in higher tiers (Tier 2 or greater). In order to reduce the occurrence of
shuffle operations and to take advantage of repeated accesses of certain cartridges,
the role of
cartridge cache is assigned to all single-deep (Tier 0) slots in an HD
library. In order to maintain efficient shuffle operations, the library performs a load
balancing of the tiers, which stores cartridges across all HD slots in the library
string. In other words, all HD slots are filled to a minimum tier level until that tier
Figure 6. The HD frame (left) and top-down view of row in an HD frame (right)
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IBM System Storage TS3500 Tape Library with ALMS: Introduction and Planning Guide