Users Guide

● Example C—You have two 10Gb host NICs, and are connecting to a volume on members with one 10Gb Ethernet port.
The optional number of sessions is one per member, because that number will saturate the member Ethernet ports.
2. Apply any user-configured session limits.
The default behavior is to limit to two sessions per volume slice or six sessions per volume, whichever is reached first.
However, you can modify these limits, as described in Configure Multipath I/O Between a Computer and a Group.
3. Apply a per-pool throttle to ensure the group remains below 90 percent of the maximum number of allowed connections per
pool.
This throttling logic ensures the connections are equitably shared among all the pool members and all the hosts using HIT
multipathing to connect to volumes on the group. See the Dell EqualLogic PS Series Storage Arrays Release Notes for the
current configuration limits.
iSCSI sessions are distributed across all available adapters and PS Series group Ethernet ports. The EHCMService monitors
the topology of the SAN. If you change the configuration, such as modify the number of Ethernet interfaces, or move a PS
Series volume, it automatically reconfigures the MPIO DSM sessions.
The MPIO DSM and PS Series group firmware create secure CHAP credentials that enable only the EHCMService to add
iSCSI sessions to a volume. These CHAP credentials are for internal use only and are not displayed by the Group Manager
GUI or CLI.
The MPIO DSM also provides load-balancing capabilities that enable you to maximize I/O throughput. The MPIO DSM has
knowledge of the distributed nature of volumes on the PS Series group and uses this knowledge to route each I/O packet by
using the optimal path to the volume.
See the Host Integration Tools for Microsoft Release Notes for specific statements about HBA hardware and firmware.
Prerequisites for Configuring Multipath I/O DSM
Your computer must meet the following requirements to use MPIO:
● A supported version of Windows, as specified in the Host Integration Tools for Microsoft Release Notes.
● The MPIO DSM is a subordinate module running within the MPIO framework. All supported versions of Windows include the
MPIO as a service; the installer will configure and start the service.
● Two or more supported Gigabit Ethernet (or faster) network interface cards (NICs) or host bus adapters (HBAs). See the
Host Integration Tools for Microsoft Release Notes for more information.
● For greatest redundancy, each host adapter must be connected to a different network switch.
The PS Series group must meet the following requirements to use MPIO:
● All group members (arrays) must be running the correct firmware revision, as specified in the Host Integration Tools for
Microsoft Release Notes.
● Each PS Series group member must have at least two, and preferably three, connected and configured network interfaces.
● For greatest redundancy, connect the PS Series network interfaces to different network switches.
Consider your local network configuration. A typical iSCSI SAN configuration provides two groups of communication interfaces.
One group is dedicated to storage data traffic and a second group is dedicated to general LAN traffic, computer
intercommunication, and other purposes. These networks are usually discrete and maintained on separate subnets.
To maximize bandwidth, the MPIO DSM automatically uses any available network interfaces. When you configure MPIO DSM,
consider restricting its access to subnets dedicated to iSCSI data traffic.
Requirements for Multipath I/O
Collect the information specified in the following table.
Table 12. Configuring Multipath I/O
Prompt Description
Subnets included The IP address range for subnets (in IPv4 or IPv6 format) that you intend to use for
multipathing.
Subnets excluded The IP address range for subnets (in IPv4 or IPv6 format) that you intend to exclude from
multipathing.
Using the Multipath I/O Component 39