About Veritas Volume Manager
Veritas Volume Manager (VxVM) by Symantec is a storage management subsystem that helps you to
manage and administer the internal physical disks or LUNs from storage as logical devices called
volumes.
VxVM was a proprietary logical volume manager from Veritas but now it is part of Symantec
Corporation and it is available for a variety of operating Systems like Solaris, Windows, Linux,
AIX and HP-UX.
The latest version of VxVM is 6.0 released as of December 2011 but still we can see 5.1 version
most widely used.
Why Veritas Volume Manager?
Volume Manager creates a virtual layer of data storage and from application point of view, the
volumes appear as just physical disk partitions. These volumes have both chearacter and block
device nodes in /dev tree.
Lets discuss some of the benefits of VxVM over physical disk.
- No limits for the number of file systems (where you have only 7 slices in solaris)
- Online Administration and disk configurations without interrupting the production environments
- Multidisk Configurations(RAID)
- High Availability
- Increased Performance ans Scalability
- Load Balancing
- Disk Spanning more resilience with Layered Volumes
- Heterogeneneous Support
Storage Management in VxVM
VxVM handles storage management with the use of following two objects
Physical Objects : Physical disks, LUNs (Logical Unit Numbers)
Virtual Objects : VxVM uses multiple virtualization layers to provide distinct functionality and reduces physical limitations. When one or more physical object is brought under veritas control it creates a virtual object called Volume (top level object in the virtualization layers) . These Volumes are accessed by file systems, databases and other applications in the same way as physical disks are accessed. Volumes are made up of other virtual components (plexes and subdisks) and all these components are referred to as Virtual objects.
VxVm relies on the following constantly running daemons and kernel threads for its operation.
vxconfigd - The VxVM configuration daemon that maintains disk and disk group configurations and communicates configuration changes to kernel
vxiod - VxVM I/O kernel threads provide extended I/O operations and by default 16 I/O threads are started at boot time where one thread must continue running at all times.
vxrelocd - The hot relocation daemon, that monitors for events and performs hot relocation in case redundancy is affected.
