3956-XSA IBM TS7760 Cache Drawer

The IBM 3956-XSA is the TS7760 Cache Drawer, the expansion unit for the TS7760 Cache Controller (3956-CSA) in an IBM TS7700 virtual tape system. It is a self-contained 2U enclosure that mounts in the 3952 Tape Frame and adds disk cache protected by dynamic disk pools.

Each drawer carries 12 disk drive modules of either 4 TB (3.63 TiB) or 8 TB (7.27 TiB) raw capacity. 4 TB and 8 TB modules cannot be mixed within a drawer, although a frame can hold both. With 4 TB modules, usable capacity is about 31 TB per drawer after dynamic disk pool formatting.

The drawer has two ESM cards and two AC power supplies with built-in cooling units, and it supports 256-bit AES encryption, including cryptographic erase and internal or external key management. Dynamic Disk Pools provide RAID 6 level protection while cutting rebuild times after a drive failure.

A TS7760 base frame can hold up to nine 3956-XSA drawers on one 3956-CSA controller. A TS7760 Storage Expansion Frame adds a second 3956-CSA that can attach up to 15 drawers when they hold 4 TB modules, or up to 14 when they hold 8 TB modules; one controller and its drawers form a string, and a TS7700 can have up to three strings.

The drawers pair with the 3957-VEC server of the TS7760. Field installation of an additional drawer is feature code 5659. The 3956-XSA is the TS7760 generation; the TS7770 uses the 3956-XSB drawer.