User`s guide

Chapter 2. RAID Array Controller
EK–SMCPO–UG. A01 2–21
While downloading the data, the controller responds to I/O by disconnecting (if
allowed) and waiting approximately three seconds before reconnecting and pre-
senting a BUSY status. The delay is to prevent host operating systems from
seeing too many errors and fencing off the controller.
2.9 Environmental
The controller incorporates a set of on board sensors to detect abnormal operat-
ing conditions that may affect data safety.
2.9.1 Backup Power Management
The controller must be connected to a backup battery and/or Uninterruptable
power supply (UPS) to prevent the subsystem cache from being corrupted during
unexpected losses of power. If no backup power supply is provided, the control-
ler will remain off-line and reject all I/O requests with a status of Check Condi-
tion/Hardware Error.
If the backup power source indicates that power may be failing, the controller’s
first step is to sound an alarm, enter write through mode and begin flushing
cache. If the backup power source reaches a critical state, the alarm frequency
increases and all host channels are disabled to prevent new requests from inter-
fering with the cache flush.
Table 2–7 shows how the controller reacts to the power supplies.
Table 2–7 Backup Power Management
UPS Status
Battery Status
OFFLINE
(Not Installed)
NORMAL WARNING
(AC Lost)
SEVERE
(2-Min. Warning)
OFFLINE
(Not Installed)
OFFLINE NORMAL SEVERE OFFLINE
NORMAL
NORMAL NORMAL WARNING WARNING
WARNING
SEVERE WARNING WARNING SEVERE
SEVERE
OFFLINE WARNING SEVERE OFFLINE
NORMAL
•
No Alarms
•
Normal I/O