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
Automatic plex reattachment
When a mirror plex encounters irrecoverable errors, Veritas Volume Manager (VxVM) detaches the plex from the mirrored volume. By default, VxVM automatically reattaches the affected mirror plexes when the underlying failed disk or LUN becomes visible. When VxVM detects that the device is online, the VxVM volume components on the involved LUN are automatically recovered, and the mirrors become usable.
VxVM uses the DMP failed LUN probing to detect when the device has come online. The timing for a reattach depends on the dmp_restore_interval, which is a tunable parameter. The number of LUNs that have reconnected may also affect the time required before the plex is reattached.
VxVM does not automatically reattach plexes on site-consistent volumes.
When VxVM is installed or the system reboots, VxVM starts the vxattachd daemon. The vxattachd daemon handles automatic reattachment for both plexes and sites. The vxattachd daemon also initiates the resynchronization process for a plex. After a plex is successfully reattached, vxattachd notifies root.
To disable automatic plex attachment, remove vxattachd from the start up scripts. Disabling vxattachd disables the automatic reattachment feature for both plexes and sites.
In a Cluster Volume Manager (CVM) the following considerations apply:
If the global detach policy is set, a storage failure from any node causes all plexes on that storage to be detached globally. When the storage is connected back to any node, the vxattachd daemon triggers reattaching the plexes on the master node only.
The automatic reattachment functionality is local to a node. When enabled on a node, all the disk groups imported on the node are monitored. If the automatic reattachment functionality is disabled on a master node, the feature is disabled on all shared disk groups and private disk groups imported on the master node.
The vxattachd daemon listens for "dmpnode online" events using vxnotify to trigger its operation. Therefore, an automatic reattachment is not triggered if the dmpnode online event is not generated when vxattachd is running. The following are typical examples:
Storage is reconnected before vxattachd is started; for example, during reboot.
In CVM, with active/passive arrays, if all nodes cannot agree on a common path to an array controller, a plex can get detached due to I/O failure. In these cases, the dmpnode will not get disabled. Therefore, after the connections are restored, a dmpnode online event is not generated and automatic plex reattachment is not triggered.
These CVM considerations also apply to automatic site reattachment.