System Components
96-30065-001 Rev. A0
DataDirect Networks EF4024 FC RAID System Setup Guide | 13
1.5
CompactFlash
During a power loss or controller failure, data stored in cache is saved off to non-volatile
memory (CompactFlash). The data is restored to cache, and then written to disk after the
issue is corrected. To protect against writing incomplete data to disk, the image stored on the
CompactFlash is verified before committing to disk.
The CompactFlash card is located at the midplane-facing end of the controller module as
shown in
Figure 7
. It is used for cache recovery only.
CAUTION :
The CompactFlash card should only be removed for transportable
purposes. To preserve the existing data stored in the CompactFlash, you
must transport the CompactFlash from the failed controller to the
replacement controller. Failure to do so 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. Contact DDN Support for guidance
on replacement procedure.
IMPORTANT:
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 (subject to volume write optimization setting).
1.6
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 power 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
flashes at a rate of 1/10 second on and 9/10 second off.
Figure 7. CompactFlash Card in Controller Module
CompactFlash Card
