Users Guide

Excluding a Subnet or Adapter From MPIO

Use the rswcli --mpio-exclude (or rswcli -E) command to select the subnets or adapters to exclude from MPIO. You can

specify a subnet, an adapter identified by a user-defined string, an IP address, or a MAC address. Dell recommends using a subnet or

adapter name based on inclusion/exclusion rules.

Including or Excluding Specific Host NICs

Include or exclude a host NIC with the IP address of the NIC and a netmask of 255.255.255.255:

# ip addr show eth1

3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP

qlen 1000

link/ether 08:00:27:31:25:55 brd ff:ff:ff:ff:ff:ff

inet x.x.x.xx/16 brd xx.xxx.255.255 scope global eth1

# rswcli --mpio-exclude --net x.x.x.xx --mask 255.255.255.255

Processing mpio-exclude command...

Adding x.x.x.xx - 255.255.255.255 to exclude list

The mpio-exclude command succeeded.

Configuring I/O Path Selection

HIT/Linux provides configurable parameters that let you establish path selection policy for the middle tier multipath device. These

parameters set load balancing policy and determine number of I/Os to send on each path before switching paths.

Load Balancing Policy

The default load balancing parameter (--mpio-parameters --dlb) lets you specify the default load balancing policy for MPIO:

Round Robin (RR) or Least Queue Depth (LQD). The RR policy rotates among each path to the member sending a fixed number of I/Os

to each. The LQD (or queue-length) policy considers the number of outstanding I/Os on that path.

Each load balancing policy is implemented by a path selector kernel module. Availability of path selectors depends on your kernel version. If

available, LQD is the default policy. If not, HIT/Linux uses RR as the default policy.

You can set the load balancing parameter by editing the eql.conf file or with the following RSWCLI command:

# rswcli --mpio-parameters --dlb LQD|RR

I/O Scheduling

The I/O per path parameter lets you specify the number of I/Os to send on each path before switching paths.

I/O scheduling is performed above the multipath layer, at the dm-switch layer. The I/O per path parameter (--mpio-parameters

--ios) defaults to a value of 16. You can adjust this value in the eql.conf file or with the following RSWCLI command:

# rswcli --mpio-parameters --ios=1-1000

Setting Volume-Specific Configuration

Parameters

The configuration parameters in the MPIO Parameters section are global settings applied to all volumes. The ehcmd command supports

volume-specific settings for the following parameters:

• EnableMPIO

• IOPerPath

Configuring Multipath I/O Devices