Dell EMC PowerVault ME484, Руководство пользователя

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Figure 34. CompactFlash memory card
1 CompactFlash memory card (installed/removed) 2 IOM viewed from back (midplane-facing orientation)
In single-controller configurations (supported with 2U24/2U12 chassis), if the controller has failed or does not start, and the Cache Status
LED is on or blinking, the CompactFlash should be transported to a replacement controller to recover data not flushed to the disk.
CAUTION: For single-controller configuration only, to preserve the existing data stored in the CompactFlash, you must transport
the CompactFlash from the failed controller to the replacement controller. This procedure is outlined in the Dell EMC ME4 Series
Storage System Owner's Manual within the procedure for replacing a controller module. Failure to use this procedure will result
in the loss of data stored in the cache module. The CompactFlash must stay with the same enclosure. If the CompactFlash is
used/installed in a different enclosure, data loss/data corruption will occur.
NOTE: In dual-controller configurations featuring one healthy partner controller, there is no need to transport failed controller
cache to a replacement controller because the cache is duplicated between the controllers, provided that volume cache is set to
standard on all volumes in the pool owned by the failed controller.
Supercapacitor pack
To protect controller module cache in case of power failure, each controller enclosure model is equipped with supercapacitor technology, in
conjunction with CompactFlash memory, built into each controller module to provide extended cache memory backup time. The
supercapacitor pack provides energy for backing up unwritten data in the write cache to the CompactFlash, in the event of a power failure.
Unwritten data in CompactFlash memory is automatically committed to disk media when power is restored. In the event of power failure,
while cache is maintained by the supercapacitor pack, the Cache Status LED blinks at a rate of 1/10 second on and 9/10 second off.
Controller failure when a single-controller is
operational
This topic can apply to 2U single controllers if that controller fails, or 2U and 5U dual controllers in the event that one of the controllers is
down and the remaining controller fails. 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.
Storage system hardware 31