EMC Symmetrix DMX-3

172
EMC Symmetrix DMX-3 Product Guide
Data Integrity, Availability, and Protection
correct operation by monitoring the battery condition, charger states,
and by providing status updates to the Communications and
Environmental Control Module (XCM).
Symmetrix power
failure on mainframe
channels
When a power failure occurs, all directors send a unit check status
with the environmental data-present bit set to all channels (error code
047A). Power switches immediately to the backup battery, and the
Symmetrix system continues to operate normally. When the battery
timer window elapses, the Symmetrix system presents SCU busy to
prevent the host system from writing or reading any data at the unit.
The Symmetrix system destages any fast write data still in global
memory to disk, spins down the disk drives and retracts the heads,
and powers down, turning off the battery at that time. The
Symmetrix system will respond not operational to the host after it
powers down.
Symmetrix power
failure on open
systems channels
When a power failure occurs, power switches immediately to the
BBU modules and the Symmetrix system continues to operate
normally. When the battery timer window elapses, the Symmetrix
system presents a busy status to prevent the host system from writing
or reading any data at the unit. The Symmetrix system destages any
Fast Write data still in global memory to disk, spins down the disk
drives and retracts the heads, and powers down, turning off the
battery at that time. The Symmetrix system will not respond to SCSI
commands after it powers down.
Nondisruptive
component
replacement
Symmetrix DMX systems implement a modular design with a low
parts count that improves serviceability by allowing nondisruptive
component replacement, should a failure occur. The low parts count
minimizes the number of failure points. The Symmetrix DMX
features concurrent maintenance of all major components, including:
◆ Channel directors
◆ Disk directors
◆ Global memory directors
◆ Disk adapters
◆ Channel adapters
◆ Disk drives
◆ Cooling fan modules
◆ Communications and Environmental Control (XCM) modules
◆ Power supplies
◆ Power Distribution Units (PDU)
◆ Power Distribution Panels (PDP)