50
System overview
4-When port is down, both LEDs are off.
Figure 42 LEDs: DS2200 SAS controller module (HD mini-SAS)
NOTE:
When a Link Status LED is lit, it remains so, even if the controller is shut down via the SMC or the CLI.
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
).
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
Table 6 Cache Status LED – power on behavior
Item
Display states reported by Cache Status LED during power on sequence
Display state
0
1
2
3
4
5
6
7
Component
VP
SC
SAS BE
ASIC
Host
Boot
Normal
Reset
Blink pattern On 1/Off 7 On 2/Off 6 On 3/Off 5 On 4/Off 4 On 5/Off 3 On 6/Off 2 Solid/On
Steady
