EMC Symmetrix DMX-3, Product Manual

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216 EMC Symmetrix DMX-3 Product Guide
Data Integrity, Availability, and Protection
• The failed drive is set to not ready.
• After the permanent sparing process completes, all system
features are available.
6. When the failed drive is replaced, the CE issues commands for
the Symmetrix system to place this drive in the spare pool,
making them available should another volume fail in the future.
EMC Customer Service is usually able to replace a failed drive within
four hours. The time it takes to replace and resynchronize a failed
drive within a RAID 5 group depends on the I/O activity to the
logical volumes, the disk drive, and the disk capacity. This time can
be significantly reduced by implementing permanent sparing.
Note: “EMC Certified Data Erasure for Symmetrix Disks” on page 186
contains information on how this feature works with permanent sparing.
Dynamic sparing Dynamic sparing provides incremental protection against failure of a
second disk during the time a disk is taken offline and when it is
ultimately replaced and resynchronized. The dynamic sparing
function determines when a logical volume is about to fail, and
copies the contents of the disk drive on which that volume resides to
an available spare without any interruption in processing (
Figure 49
on page 217 ). The Symmetrix system notifies the EMC Customer
Support Center of this event with an Environmental-Data Present
error, and then uses the spare until the device can be replaced.