EMC Symmetrix DMX-3, Product Manual

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Overview 161
Data Integrity, Availability, and Protection
Symmetrix Remote
Data Facility (SRDF)
EMC’s SRDF family of software products help companies manage
planned data center events such as scheduled maintenance, daily
backups, migrations, and application testing, as well as recovery
from unplanned outages such as disasters. The following sections
briefly describe the SRDF product offerings.
The “SRDF family of products” on page 221 contains additional
information on SRDF applications.
Note: Each of the SRDF product offerings is sold under a separate license by
EMC. For more in-depth information about SRDF, refer to the EMC
Symmetrix Remote Data Facility (SRDF) Product Guide. Contact your local EMC
Sales Representative for specific information on availability of each of the
SRDF products.
Permanent sparing
Permanent sparing is an automatic data protection option for all
Symmetrix DMX-3 systems. It is used in conjunction with mirroring,
RAID 5, RAID 6, or SRDF. The permanent sparing process identifies
an identical drive in a good location and begins to move the data to the
new drive. If there is no drive available in a good location, the
dynamic sparing process is followed.
After the permanent sparing process completes, all system features
are available, and the Symmetrix returns to normal operation without
waiting for a CE to replace the failed drive. The failed drive is left as a
not ready drive. When the failed drive is replaced, the CE issues
commands for the Symmetrix system to place the drive in the spare
pool, making it available should another volume fail in the future.
Note: “Permanent sparing” on page 213 provides more information on the
permanent sparing option.
Dynamic sparing Dynamic sparing is a data protection option for all Symmetrix
DMX-3 systems. It is used in conjunction with mirroring, RAID 5, or
SRDF. (Dynamic sparing cannot be used with RAID 6.) If permanent
sparing cannot be used, then dynamic sparing is invoked. Dynamic
sparing limits the exposure after drive failure and before drive
replacement. With dynamic sparing, the Symmetrix system maintains
a pool of spare drives that are used only when the system detects a
potentially failing device. The dynamic sparing process moves the
data and uses the spare until the original device can be replaced.
Note: Contact your local EMC Sales Representative for specific Dynamic
sparing configuration rules or “Dynamic sparing” on page 216 .