Getting Started
DataDirect Networks EF2800 FC RAID Storage System User Guide (V 1.0)
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2.10 Understanding how the SMs Work Together
The following terms are associated with how the pair of SM modules
work together:.
• SM A and B: One SM module is designated as SM module A (right
hand module when viewed from the rear) and the other is
designated as SM module B (left hand module). When both SM
modules start at the same time, they exchange information related
to their current configuration and the ownership of resources. The
time and date of SM module B is synchronized with that of SM
module A
• Failback: The act of returning ownership of SM module resources
from the surviving SM to a previously failed or offline (but now
active) SM module. The resources include disk arrays, cache data,
and host ID information.
• Failover: The act of temporarily transferring ownership of SM
module resources from a failed or offline SM to the surviving SM
module. The resources include disk arrays, cache data, and host ID
information.
• Force offline: One SM module can force the other SM offline by
resetting it and taking it offline. You can also force an SM module
offline by pressing the latches on the SM module’s handles or using
SAM.
• Other: The opposite SM module from the one currently being used
(that is, not the SM module you are connected to). In most cases,
you can perform all SM module functions from one SM module.
• Ownership: A single SM module has ownership of the following
resources: arrays and dedicated spares. When an SM module fails,
the other SM module assumes temporary ownership of its
resources.
• Put offline: When you use SAM to gracefully take an SM module
offline.
• Put online: When you use SAM to put the other SM module online.
The other SM module will restart and attempt to come online.
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