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7 Dell Storage PS Series Arrays: Scalability and Growth in Virtual Environments | TR1072
In larger environments, these additional MPIO connections need to be taken into account at design time and
as the environment scales. Here is an example of how quickly connections can be consumed: Assume there
is a 16 node cluster connecting to 20 volumes in a single storage pool with 3 PS arrays. That equation looks
like the following:
16 hosts x 6 session connections (2 sessions per volume slice x 3 members) x 20 volumes = 1920
connections to the pool
This far exceeds the validated number of connections per pool. To control and avoid excessive consumption
of connections, the MEM and DSM can be customized to scale down the number of connections made to
volumes. As mentioned, by default these MPIO modules will make two connections per member and up to six
connections per volume. Sometimes it may be necessary to scale down these default limits to reduce the
number of connections made to a PS Series pool or Group. In this case, it is recommended to start by
changing the Max sessions per volume slice setting from 2 to 1. This will reduce the amount of connections
made to a volume in half, with only minimal impact on performance. See the following example for a 2-node
cluster volume with the default setting of 2, compared to changing the setting to 1.
Connections using default MPIO DSM settings
Connections setting Max sessions per volume slice changed from 2 to 1