Appendix A
LED descriptions
79
Cache Status LED details
Power on/off behavior
During power on, discrete sequencing for power on display states of internal components is reflected by blinking
patterns displayed by the Cache Status LED as shown in the table.
Item
Display states reported by Cache Status LED during power on sequence
Display state
0
1
2
3
4
5
6
7
Component
VP
ASIC
SAS BE
SC
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
Table 27 Cache Status LED — power on behavior
NOTE Component acronyms used for Cache Status LED states:
l
VP = Voltage Plane (stage 0)
l
ASIC = Application-specific Integrated Circuit (stage 1)
l
SAS BE = Enclosure's backend SAS system interface (stage 2)
l
SC = Storage controller: processor located in controller module (stage 3)
After 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
contains data that has not been written to disk, the supercapacitor pack provides backup power to flush (copy) data
from write cache to nonvolatile memory. When cache flush is complete, the cache transitions into self-refresh mode. See
also
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 nonvolatile
memory, 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 nonvolatile memory 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 nonvolatile memory the next time the controller shuts down.
CAUTION 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 nonvolatile memory.
MSA 1060/2060/2062 PCMs—rear panel layout
MSA 2060/2062 Storage enclosures support either two redundant AC PCMs or two redundant DC PCMs as described
below. MSA 1060 Storage enclosures support redundant AC PCMs exclusively.
TIP Cross reference the enlarged LED icon labels with the callout numbers when reading table entries.