Network LVM-storage

The virtual disk of a virtual machine is the HDD image. Virtual disks are stored in a local or network storage. A network LVM-storage is similar to a common lvm except for some details. However, the physical volume where a group of volumes is located is a network device. 

This article describes how to configure the network LVM-storage. For more information please refer to the article Network storages.

Peculiarities

When creating a virtual machine, on the same cluster node a virtual disk is created, and it will be accessible on all the cluster node. It will be active only on one node.

When migrating a virtual machine, the virtual disk will not copy but will activate on the target node. On the source node, the disk will be disabled.

Example of configuration using open-iscsi

Network storage configuration

1. install iSCSI:

   # yum install scsi-target-utils

2. Configure lvm:

   # pvcreate /dev/sda2
     Physical volume "/dev/sda2" successfully created
   # vgcreate vg0 /dev/sda2
     Volume group "vg0" successfully created

3. Configure the tgtd configuration file:

   # cat /etc/tgt/targets.conf
   
   ...
   <target iqn.2014-04.net.ispsystem.nlvm:storage.nlvm>
       backing-store /dev/sda2
       initiator-address 10.1.1.1 #IP-адрес узла кластера
       initiator-address 10.1.1.2
       initiator-address 10.1.1.3
   </target>
   ...
   

4. Restart tgtd:

   # service tgtd restart
     Stopping SCSI target daemon: [ OK ]
     Starting SCSI target daemon: [ OK ]

5. Add iptables rules, if needed:

   iptables -I INPUT 1 -p tcp --dport 3260 -j ACCEPT
   service iptables save

Connecting to cluster nodes

Connect the disk on each cluster node

iscsiadm -m discovery -t st -p 10.1.2.1
iscsiadm -m node --login -p 10.1.2.1

Once completed you can add a "network LVM" storage named vg0 into VMmanager.