Release Notes

Using MEM with Virtual Volumes
18 Configuring and Installing the PS Series Multipathing Extension Module for VMware vSphere and PS Series | TR1074
7 Using MEM with Virtual Volumes
VMware introduced the Virtual Volumes (vVols) feature with vSphere 6.0. It enables per-VM granularity for
many storage-related tasks, as opposed to per-volume granularity. While vVols do not require MEM, the
inclusion of MEM in a PS Series vVol environment provides more efficient routing of I/O, reduced latency, and
increased bandwidth utilization. For additional information on Virtual Volumes, see VMware vSphere Virtual
Volumes on Dell PS Series.
7.1 MEM configuration and installation
While vVol changes many things when it comes to architecting a vSphere environment, it does not alter the
creation of the iSCSI vSwitch for multipathing, or the installation process of the MEM.VIB.
7.2 Access controls
One aspect that has changed with vVols is access controls. With traditional volumes, access to a volume is
managed through an access control list or access control policy, on a per-volume basis. However, with vVols
volumes, this no longer applies. Access is restricted by an access control list on the protocol endpoint, and
managed from the PS Series Virtual Storage Manager (VSM) plugin for vCenter. For detailed instructions on
vVol access controls, see the document, Dell Virtual Storage Manager: Installation Considerations and Local
Data Protection.
7.3 Virtual Volumes impact on iSCSI connection count
With traditional VMFS datastores, the iSCSI connection terminated at the individual volume, but with vVols,
this has changed. The iSCSI connection now terminates at the protocol endpoint, resulting in a lowering of the
iSCSI connection count, regardless of the number of storage containers or the number vVol-based virtual
machines. With MEM and vVols, the iSCSI connection count is now simply one iSCSI connection per
VMkernel/PS Series member pair, with a minimum of at least two iSCSI connections from each host to the
ESXi host to the protocol endpoint. The formula can be expressed as:
Number of VMkernel ports used for iSCSI x Number of members in group x two sessions per member
For example, if there are three PS6210 arrays, and each host is configured with two VMkernel ports for iSCSI,
then six iSCSI connections will be created from each host.
As with all rules, there are exceptions. With the PS6110, PS4110, and PS-M4110 arrays, if they are in a
single-member pool, MEM will create two iSCSI connections to the protocol endpoint for redundancy. With
two or more such members in the pool, MEM will create a single iSCSI connection per member, resulting in
one iSCSI connection being created per member to the protocol endpoint.
When mixing traditional volumes and virtual volumes, the iSCSI connection pool limit applies to the combined
total of iSCSI connections from traditional volumes and the iSCSI connection to the protocol endpoint.