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STEC has developed an innovative technique to avoid
data loss or corruption in case of power loss, called
Power Down Recovery.
During the course of each write operation, the controller
maintains multiple flags and pointers to monitor the
start and end of each phase. Both are used to monitor
the write/erase progress and show which phase of the
process has been completed or is in progress. If the
operation is interrupted by a power failure, the controller
will use the pointers to indicate the last block that
was accessed. By reading the start and completion flags
on that block, the controller will be able to detect
where a sector write was interrupted.
In case the page only shows the start flag, but not
the completion flag, the controller will consider the
data as not reliable. As such, all the data of that
block, apart from the uncompleted sector, will be transferred
to a new block. The old block will be erased and transferred
to the pool of spare blocks. This mechanism protects
the original data from being overwritten by incomplete
or corrupted data.
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