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Shutting Down a Clustered Configuration (CLI)
and LUN must be shared via the appropriate service(s). The amount of time required to perform
these activities for a single share or LUN is very small - on the order of tens of milliseconds -
but with very large share counts this can contribute significantly to takeover times. Keeping the
number of shares relatively small - a few thousand or fewer - can therefore reduce these times
considerably.
Failback time is normally greater than takeover time for any given configuration. This is
because failback is a two-step operation: first, the source appliance exports all resources of
which it is not the assigned owner, then the target appliance performs the standard takeover
procedure on its own assigned resources only. Therefore it will always take longer to failback
from controller A to controller B than it will take for controller A to take over from controller
B in case of failure. This additional failback time is much less dependent upon the number of
disksets being exported than is the takeover time, so keeping the number of shares and LUNs
small can have a greater impact on failback than on takeover. It is also important to keep in
mind that failback is always initiated by an administrator, so the longer service interruption it
causes can be scheduled for a time when it will cause the lowest level of business disruption.
Estimated times cited in this section refer to software/firmware version 2009.04.10,1-0.
Note -
Other versions may perform differently, and actual performance may vary. It is important to test
takeover and its exact impact on client applications prior to deploying a clustered appliance in a
production environment.
Related Topics
"Shutting Down a Clustered Configuration (CLI)" on page 199
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Configuring the Appliance
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