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.

Figure 1 shows the inside of an HD frame from the side. The single-deep slots on the door side  2  of HD frames are referred to as Tier 0 slots. The deep cell  1  contain Tier 1 thru Tier 5.

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.

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 cartridges in lower tiers into the gripper (or other available slots) to access cartridges in higher tiers (Tier 2 or greater). To reduce shuffle operations and 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. To maintain efficient shuffle operations, the library uses load balancing to store 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 is full across the library.