EMC Symmetrix DMX-3

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EMC Symmetrix DMX-3 Product Guide
Data Integrity, Availability, and Protection
Enginuity supports a direct copy mode between the spare and the
failing member. For example, once the failing drive is replaced,
Enginuity will avoid rebuilding the data to the new drive. Instead, it
will copy the tracks (both data and parity) directly from the spare to
the new drive. This is a much faster way of validating the new drive.
The Symmetrix system has a sense of copy direction. When a spare is
invoked, the default copy direction is from the failing member to the
spare. The spare has a mirror number of its own that never changes.
Note: Dynamic sparing cannot be used with RAID 6 volumes.
Dynamic sparing with
remotely mirrored
pairs (SRDF)
When the dynamic sparing option is invoked for a remotely mirrored
SRDF pair, the Symmetrix system automatically activates an available
spare in the Symmetrix unit containing the failing device and copies
data from the failing device to the spare. The Symmetrix system
continues processing I/Os (with the spare functioning as one of a
mirrored pair with the failing device), and its remote mirror
continues with no interruption in operation. If the Symmetrix system
cannot copy all data from the failing device to the spare, it retrieve the
unavailable data from the good member of the remote pair.