Veritas™ Volume Manager Administrator's Guide
- Understanding Veritas Volume Manager
- VxVM and the operating system
- How VxVM handles storage management
- Volume layouts in VxVM
- Online relayout
- Volume resynchronization
- Dirty region logging
- Volume snapshots
- FastResync
- Provisioning new usable storage
- Administering disks
- Disk devices
- Discovering and configuring newly added disk devices
- Discovering disks and dynamically adding disk arrays
- How to administer the Device Discovery Layer
- Changing the disk-naming scheme
- Adding a disk to VxVM
- Rootability
- Displaying disk information
- Removing disks
- Removing and replacing disks
- Administering Dynamic Multi-Pathing
- How DMP works
- Administering DMP using vxdmpadm
- Gathering and displaying I/O statistics
- Specifying the I/O policy
- Online dynamic reconfiguration
- Reconfiguring a LUN online that is under DMP control
- Creating and administering disk groups
- About disk groups
- Displaying disk group information
- Creating a disk group
- Importing a disk group
- Moving disk groups between systems
- Handling cloned disks with duplicated identifiers
- Handling conflicting configuration copies
- Reorganizing the contents of disk groups
- Destroying a disk group
- Creating and administering subdisks and plexes
- Displaying plex information
- Reattaching plexes
- Creating volumes
- Types of volume layouts
- Creating a volume
- Using vxassist
- Creating a volume on specific disks
- Creating a mirrored volume
- Creating a striped volume
- Creating a volume using vxmake
- Initializing and starting a volume
- Using rules and persistent attributes to make volume allocation more efficient
- Administering volumes
- Displaying volume information
- Monitoring and controlling tasks
- Reclamation of storage on thin reclamation arrays
- Stopping a volume
- Resizing a volume
- Adding a mirror to a volume
- Preparing a volume for DRL and instant snapshots
- Adding traditional DRL logging to a mirrored volume
- Enabling FastResync on a volume
- Performing online relayout
- Adding a RAID-5 log
- Creating and administering volume sets
- Configuring off-host processing
- Administering hot-relocation
- How hot-relocation works
- Moving relocated subdisks
- Administering cluster functionality (CVM)
- Overview of clustering
- Multiple host failover configurations
- CVM initialization and configuration
- Dirty region logging in cluster environments
- Administering VxVM in cluster environments
- Changing the CVM master manually
- Importing disk groups as shared
- Administering sites and remote mirrors
- About sites and remote mirrors
- Fire drill - testing the configuration
- Changing the site name
- Administering the Remote Mirror configuration
- Failure and recovery scenarios
- Performance monitoring and tuning
- Appendix A. Using Veritas Volume Manager commands
- Appendix B. Configuring Veritas Volume Manager
Dirty region logging in cluster environments
Dirty region logging (DRL) is an optional property of a volume that provides speedy recovery of mirrored volumes after a system failure. DRL is supported in cluster-shareable disk groups. This section provides a brief overview of how DRL behaves in a cluster environment.
In a cluster environment, the VxVM implementation of DRL differs slightly from the normal implementation.
A dirty region log on a system without cluster support has a recovery map and a single active map. A CVM DRL, however, has a single recovery map per cluster and one active map per cluster node.
The dirty region log size in clusters is typically larger than in non-clustered systems, as it must accommodate a recovery map plus active maps for each node in the cluster. The size of each map within the dirty region log is one or more whole blocks. The vxassist command automatically allocates a sufficiently large dirty region log for the size of the volume and the number of nodes.
It is possible to reimport a non-shared disk group (and its volumes) as a shared disk group in a cluster environment. However, the dirty region logs of the imported disk group may be considered invalid and a full recovery may result.
If a shared disk group is imported as a private disk group on a system without cluster support, VxVM considers the logs of the shared volumes to be invalid and conducts a full volume recovery. After the recovery completes, VxVM uses DRL.
The cluster functionality of VxVM can perform a DRL recovery on a non-shared volume. However, if such a volume is moved to a VxVM system with cluster support and imported as shared, the dirty region log is probably too small to accommodate maps for all the cluster nodes. VxVM then marks the log invalid and performs a full recovery anyway. Similarly, moving a DRL volume from a two-node cluster to a four-node cluster can result in too small a log size, which the cluster functionality of VxVM handles with a full volume recovery. In both cases, you must allocate a new log of sufficient size.
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