March 2013 Dell EqualLogic Configuration Guide v14.1 11-111
System controllers
The system contains dual active-active controller nodes with large onboard battery-backed caches
and 24 GB of battery protected memory per node. They operate in an active-active environment
mirroring the system’s cache. Each node regularly monitors the BPS battery status. They require the
BPS to maintain a minimum level of power stored during normal operation to ensure that they can
execute a proper shutdown procedure in the event of power interruption.
Backup power supply
The BPS is designed to provide power necessary for controllers to execute a proper shutdown
procedure. The BPS also enables the FS7500 controllers to use their onboard cache as NVRAM. This
provides the clustered solution with enough time to write all the data from the cache to disk in the
event a controller node experiences a loss of power.
11.4 FS7500 file system operation on controller failover
In the FS7500 system, writes to one controller node cache are mirrored to the other controller node
cache before the write is acknowledged and committed. This prevents loss of any in-flight write I/O if
a controller failure occurs. If a controller node failure occurs the cluster is put in journal mode. This
triggers all I/O normally written to the mirror cache to be written to a journal file instead. Client load
balancing in the FS7500 make this process transparent from a client point of view.
11.5 FS7600 components
The FS7600 and FS7610 NAS Appliance consist of two hot pluggable redundant NAS controllers per
appliance, redundant hot pluggable power supplies, and fans. Each NAS controller contains a built-in
battery backup to protect cache in case of controller power failure. The system components are
shown in Figure 35 and Figure 36.
Figure 35 Rear view of the FS7600 NAS appliance
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