Controller Failure When A Single-Controller Is Operational; Cache Status Led - Power On Behavior - Seagate RealStor 5005 Series Hardware Installation

When a controller is shut down or otherwise rendered inactive—its Link Status LED remains illuminated— falsely
indicating that the controller can communicate with the host. Though a link exists between the host and the chip on the
controller, the controller is not communicating with the chip. To reset the LED, the controller must be power-cycled.
Cache Status LED details
Power on/off behavior
The storage enclosure's unified CPLD provides integrated Power Reset Management (PRM) functions. During power on,
discrete sequencing for power on display states of internal components is reflected by blinking patterns displayed by the
Cache Status LED (see
Table 5 Cache Status LED – power on behavior
Item
Display state
Component
Blink pattern
Once the enclosure has completed the power on sequence, the Cache Status LED displays Solid/On (Normal), before
assuming the operating state for cache purposes.
Cache status behavior
If the LED is blinking evenly, a cache flush is in progress. When a controller module loses power and write cache is dirty
(contains data that has not been written to disk), the supercapacitor pack provides backup power to flush (copy) data
from write cache to CompactFlash memory. When cache flush is complete, the cache transitions into self-refresh mode.
If the LED is blinking momentarily slowly, the cache is in a self-refresh mode. In self-refresh mode, if primary power is
restored before the backup power is depleted (3–30 minutes, depending on various factors), the system boots, finds data
preserved in cache, and writes it to disk. This means the system can be operational within 30 seconds, and before the
typical host I/O time-out of 60 seconds, at which point system failure would cause host-application failure. If primary
power is restored after the backup power is depleted, the system boots and restores data to cache from CompactFlash,
which can take about 90 seconds. The cache flush and self-refresh mechanism is an important data protection feature;
essentially four copies of user data are preserved: one in controller cache and one in CompactFlash of each controller.
The Cache Status LED illuminates solid green during the boot-up process. This behavior indicates the cache is logging all
POSTs, which will be flushed to the CompactFlash the next time the controller shuts down.
IMPORTANT: If the Cache Status LED illuminates solid green—and you wish to shut down the controller—do so from
the user interface, so unwritten data can be flushed to CompactFlash.

Controller failure when a single-controller is operational

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 1Gbyte 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 blinks at a rate of 1/10 second on and 9/10 second off.
30 System overview
Table 5).
Display states reported by Cache Status LED during power on sequence
0 1
VP SC
On 1/Off 7 On 2/Off 6 On 3/Off 5 On 4/Off 4 On 5/Off 3 On 6/Off 2
2 3
SAS BE Moose
4 5
Host Boot Normal
Solid/On
6 7
Reset
Steady