Release Notes

Advanced iSCSI connection configuration parameters
16 Configuring and Installing the PS Series Multipathing Extension Module for VMware vSphere and PS Series | TR1074
6.2 Decreasing the default values
In large configurations, reduce the number of iSCSI connections if the limits of the array firmware are
exceeded. This can be achieved by:
• Reducing the number of volumes: By increasing the size of a given volume, more virtual machines
can reside on it, thereby reducing the total number of volumes needed.
• Reconfiguring larger clusters into multiple smaller clusters: By splitting a large cluster into smaller
clusters, the number of hosts accessing particular volumes is reduced, thereby reducing the number
of iSCSI connections consumed.
• Altering the configuration of the PS Series group: Reducing the number of PS Series members per
pool, and increasing the number of pools, will increase the number of available iSCSI connections.
These changes typically take some time to implement. Altering the EHCM parameters provides a means of
quickly reducing the iSCSI connection to be within limits. However, depending on the overall environment
configuration and I/O workload, a drop in overall performance may be observed.
• totalsessions: This parameter is defaulted to a maximum of 512, and can be lowered to 64. It is the
maximum number of iSCSI connections that EHCM will create from this individual ESXi host to all PS
Series arrays. If an additional volume is added to the host, EHCM automatically rebalances the
sessions to include the new and existing volumes, without consuming more than the totalsessions
limit.
• volumesessions: This parameter is defaulted to a maximum of 6, and can be lowered to 1. It is the
maximum number of iSCSI connections that EHCM will make from this individual ESXi host to each
individual PS Series volume, regardless of the number of array members the volume may span as the
group expands. This value applies to all volumes that the host accesses, and cannot be specified to
affect only particular volumes. As additional members are added to the pool, and volumes are
distributed to include this new member, EHCM creates additional sessions to the volume within this
limit.
• membersessions: This parameter is defaulted to a maximum of 2, and can be lowered to 1. It is the
number of iSCSI connections that EHCM makes from this individual ESXi host to the portion of a
volume that resides on an individual PS Series member. Setting membersessions to 1 will halve the
iSCSI connection count from the ESXi host to the array. However, this effectively disables the Least
Queue Depth part of the MPIO algorithm, as there is one queue to each portion of the volume. The
Intelligent Routing part of the algorithm remains in use, so I/O requests will be efficiently directed to
the appropriate member.
Note: Similar default values for VMware
®
vSphere
®
Virtual Volumes™ (vVols) are defined in ehcmd.conf. See
the product documentation for details.
6.3 Setting the EHCM configuration values under vSphere
PS Series arrays have added a number of commands that can be used to control and report on the status of
the MEM. It is through these commands that the EHCM parameters are changed.
The esxcli command can be executed remotely from the vMA, CLI, or directly on the ESXi host. The syntax of
this command is:
esxcli equallogic param set --name=parameter_name
--value=parameter_value