Cache Module; Power/Uid Module - HP StorageWorks 9100 - Extreme Data Storage System User Manual

Cache module

To enable faster data access from disk storage, the cache module performs two types of caching:
• Posted-write caching—the controller writes user data in the cache memory on the module rather
than directly to the drives. Later, when the storage system is idle, the controller writes the data to
the drive array.
• Read-ahead caching—the controller detects sequential array access, reads ahead into the next
sequence of data, and stores the data in the read-ahead cache. Then, if the next read access is for
the cached data, the controller immediately loads the data into system memory, avoiding the latency
of a disk access.

Power/UID module

The combined power/UID module allows you to power on/power off the enclosure, as well as identify
the device and all additional cascaded devices.
Item Description
1 UID button/LED
2 System heartbeat LED
• To illuminate the UID LEDs on this and all cascaded devices, press the UID button. UID LEDs on
the front and rear of the devices remain illuminated until the UID button is pressed a second time.
• To power on the enclosure, press and release the Power/Standby button.
• To place an enclosure in standby mode, press and hold the Power/Standby button for
approximately three seconds, or until the Power/Standby button LED changes from green to amber.
• To completely remove power from an enclosure, place the enclosure in standby mode, and then
disconnect all power cords.
NOTE:
• System power to the enclosure (and possibly other cascaded devices) does not completely shut off with
the Power/Standby button. When the enclosure is in standby mode, power is removed from most of
the electronics and components, but portions of the power supply and internal circuity remain active.
• After a power failure, the system automatically returns to the last powered state (On or Standby)
when A/C power is restored.
16 Components
Item Description
3 System fault LED
4 Power/Standby button