Configure EMC VNX Multipathing

Use multipathing to provide network-and-SP-redundancy for the iSCSI data path between the EMC VNX SAN and NCs.

WARNING

Multipathing is available only for the EMC VNX SAN.

Important

It is strongly recommended that you get your system up and running and able to create volumes and snapshots using the EMC VNX prior to configuring multipathing. Multipathing can be configured after the cloud is fully functional and will apply to any volumes attached/snapshotted after multipathing is configured. Configuring multipathing on a non-multipathed system does not require a restart of the SC, NC, or CLC.

To configure multipathing for a EMC VNX SAN:

Ensure that the mutipathd service is running on each NC:
mpathconf --enable

Configure the /etc/multipath.conf file.

Note

An example configuration for EMC VNX is installed with Eucalyptus. This file is located in /usr/share/doc/eucalyptus-3.2.0/eucalyptus.multipath.conf.example on each SC. You may need to copy that file to each NC.

Start the mutipathd service:
```
service multipathd start
```
If you modify the /etc/multipath.conf file, be sure to restart and reconfigure multipathd:
1. Restart the multipathd service:
```
service multipathd restart
```
2. Run multipathd -k:
```
multipathd -k
```
3. Enter the following commands at the multipathd interactive prompt:
```
reconfigure
quit
```
Check that the multipath udev rules file is installed by verifying that the file /etc/udev/rules.d/12-dm-permissions.rules file exists.

Set the ISCSI paths:

Note

The path specification format is iface0:ip0,iface1:ip1,...,ifaceN:ipN where iface may be re-‐used (i.e. multiple iface0 entries). Also, note that ‘iface’ is optional, you may just specify a comma-‐delimited list of IPs. Eucalyptus will detect which interfaces on the SC/NC can reach each specified IP and will use the first found. You must only specify the ‘iface’ value if you want precise control over which interfaces access which IPs. For using a single path only, just specify the IP of the iscsi data port to use on the VNX.

Note

We recommend initially getting the system working with only one path. The path values can be modified at any time to enable multipathing, so it is possible to get everything working and confirm full VNX functionality before attempting multipathing. To use one path, simply specify a single IP for each the following steps.

Set the NC paths. For example:
euca-modify-property -p mypartition.storage.ncpaths=iface0:127.0.0.1

Set the SC paths. For example:

euca-modify-property -p mypartition.storage.scpaths=iface0:127.0.0.1

Note

The NC and SC may each have different path lists, or you can optionally only enable multipathing on the NCs or SC if desire.

If you specified an iface when setting the SC paths, be sure to include a line in the eucalyptus.conf file of each NC in the cluster that defines each iface. For example:
STORAGE_INTERFACES="iface0=eth0"

Test and verify the configuration by creating (and attaching to) a volume and creating a snapshot on the partition.
If testing is successful, you can now configure multiple paths in your *.storage.ncpaths and *.storage.scpaths configuration.

Verify that multipathing is working on an NC by attaching a volume to an instance on that NC and running the following command:

 multipath -ll

This command should return output similar to the following:

mpathb (36006016098b0300080722f971b2ee211) dm-‐0 DGC,VRAID 
size=1.0G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
|-‐+-‐ policy='round-‐robin 0' prio=50 status=active
| `-‐ 6:0:0:1 sdd 8:48 active ready running
`-‐+-‐ policy='round-‐robin 0' prio=10 status=enabled
`-‐ 7:0:0:1 sdf 8:80 active ready running

You have now successfully configured multipathing for your EMC VNX SAN installation.