IBM TS4500, Introduction And Planning Manual, Page: 25 / 218

High-density technology
The TS4500 tape library offers high-density (HD), drive-capable and storage-only
frame models that are designed to greatly increase storage capacity without
increasing frame size or required floor space.
HD slots contain tape cartridges in a tiered architecture. The cartridge immediately
accessible in the HD slot is a Tier 1 cartridge. Behind that is Tier 2. The maximum
tier in an LTO HD slot is Tier 5. The maximum tier in a 3592 HD slot is Tier 4
because the 3592 tape cartridge is slightly longer than the LTO cartridge. The
single-deep slots on the door side of HD frames are referred to as Tier 0 slots. On
the left, Figure 3 shows the inside of an HD frame from the side. On the right,
Figure 3 shows a top-down view of one row of an HD frame with cartridges in
Tiers 0 (door side), 1, 2, and 3.
All HD slots are black. The location of the cartridge retention latch differentiates
LTO HD slots from 3592 HD slots. The cartridge retention latch is on the left side
of LTO HD slots and on the right side of 3592 HD slots.
Attention: The HD slots have a constant force spring for maintaining forward
pressure on the tape cartridges. Use caution when you are inserting or removing
cartridges from HD slots.
Note: The cartridge count should not exceed 99% of the reported library slot
capacity. Unused slots are required for shuffle operations.
In HD frames, the cartridge accessor runs a shuffle operation to access the
cartridges that are stored in Tier 2 and beyond. A shuffle is the process of moving
Figure 3. The HD frame (left) and top-down view of row in an HD frame (right)
Chapter 1. Overview
7