Dot Hill Systems 4524 - Controller Failure in a Single-Controller Configuration; If the Controller Has Failed or Does Not Start, Is the Cache Status LED On;Blinking; Transporting Cache; Isolating a Host-Side Connection Fault

AssuredSAN 4004 Series Setup Guide 89
Controller failure in a single-controller configuration
Cache memory is flushed to CompactFlash in the case of a controller failure or power loss. During the write
to CompactFlash process, only the components needed to write the cache to the CompactFlash are
powered by the supercapacitor. This process typically takes 60 seconds per 1 Gbyte of cache. After the
cache is copied to CompactFlash, the remaining power left in the supercapacitor is used to refresh the
cache memory. While the cache is being maintained by the supercapacitor, the Cache Status LED flashes
at a rate of 1/10 second on and 9/10 second off.
IMPORTANT: Transportable cache only applies to single-controller configurations. In dual-controller
configurations, there is no need to transport a failed controller’s cache to a replacement controller because
the cache is duplicated between the partner controllers (subject to volume write optimization setting).
If the controller has failed or does not start, is the Cache Status LED on/blinking?
Table 21 Diagnostics LED status: Rear panel “Cache Status”
NOTE: See also Cache Status LED details on page 125.
Transporting cache
To preserve the existing data stored in the CompactFlash, you must transport the CompactFlash from the
failed controller to a replacement controller using the procedure outlined in the AssuredSAN 4004
Series FRU Installation and Replacement Guide. Failure to use this procedure will result in the loss of data
stored in the cache module.
CAUTION: Remove the controller module only after the copy process is complete, which is indicated by
the Cache Status LED being off, or blinking at 1:10 rate.
Isolating a host-side connection fault
During normal operation, when a controller module host port is connected to a data host, the port’s host
link status/link activity LED is green. If there is I/O activity, the host activity LED blinks green. If data hosts
are having trouble accessing the storage system, and you cannot locate a specific fault or cannot access
the event logs, use the following procedure. This procedure requires scheduled downtime.
Answer Actions
No, the Cache LED status is off, and the
controller does not boot.
If valid data is thought to be in Flash, see Transporting cache;
otherwise, replace the controller module.
No, the Cache Status LED is off, and the
controller boots.
The system has flushed data to disks. If the problem persists,
replace the controller module.
Yes, at a strobe 1:10 rate - 1 Hz, and the
controller does not boot.
See Transporting cache.
Yes, at a strobe 1:10 rate - 1 Hz, and the
controller boots.
The system is flushing data to CompactFlash. If the problem
persists, replace the controller module.
Yes, at a blink 1:1 rate - 1 Hz, and the controller
does not boot.
See Transporting cache.
Yes, at a blink 1:1 rate - 1 Hz, and the controller
boots.
The system is in self-refresh mode. If the problem persists, replace
the controller module.