Installation guide

Chapter 22.
149
Device Mapper Multipathing and Virtual
Storage
Red Hat Enterprise Linux 6 also supports DM-Multipath and virtual storage. Both features are
documented in detail in other stand-alone books also provided by Red Hat.
22.1. Virtual Storage
Red Hat Enterprise Linux 6 supports the following file systems/online storage methods for virtual
storage:
• Fibre Channel
• iSCSI
• NFS
• GFS2
Virtualization in Red Hat Enterprise Linux 6 uses libvirt to manage virtual instances. The libvirt
utility uses the concept of storage pools to manage storage for virtualized guests. A storage pool
is storage that can be divided up into smaller volumes or allocated directly to a guest. Volumes of
a storage pool can be allocated to virtualized guests. There are two categories of storage pools
available:
Local storage pools
Local storage covers storage devices, files or directories directedly attached to a host. Local
storage includes local directories, directly attached disks, and LVM Volume Groups.
Networked (shared) storage pools
Networked storage covers storage devices shared over a network using standard protocols.
Networked storage includes shared storage devices using Fibre Channel, iSCSI, NFS, GFS2, and
SCSI RDMA protocols. Networked storage is a requirement for migrating guest virtualized guests
between hosts.
Important
For comprehensive information on the deployment and configuration of virtual storage instances
in your environment, please refer to the Virtualization Storage section of the Virtualization guide
provided by Red Hat.
22.2. DM-Multipath
Device Mapper Multipathing (DM-Multipath) is a feature that allows you to configure multiple I/O paths
between server nodes and storage arrays into a single device. These I/O paths are physical SAN
connections that can include separate cables, switches, and controllers. Multipathing aggregates the I/
O paths, creating a new device that consists of the aggregated paths.
DM-Multipath are used primarily for the following reasons: