Dynamic Multi-Pathing 7.4.1 Administrator's Guide - Linux
- Understanding DMP
- Setting up DMP to manage native devices
- About setting up DMP to manage native devices
- Displaying the native multi-pathing configuration
- Migrating LVM volume groups to DMP
- Migrating to DMP from EMC PowerPath
- Migrating to DMP from Hitachi Data Link Manager (HDLM)
- Migrating to DMP from Linux Device Mapper Multipath
- Using Dynamic Multi-Pathing (DMP) devices with Oracle Automatic Storage Management (ASM)
- Enabling Dynamic Multi-Pathing (DMP) devices for use with Oracle Automatic Storage Management (ASM)
- Removing Dynamic Multi-Pathing (DMP) devices from the listing of Oracle Automatic Storage Management (ASM) disks
- Migrating Oracle Automatic Storage Management (ASM) disk groups on operating system devices to Dynamic Multi-Pathing (DMP) devices
- Adding DMP devices to an existing LVM volume group or creating a new LVM volume group
- Removing DMP support for native devices
- Administering DMP
- About enabling and disabling I/O for controllers and storage processors
- About displaying DMP database information
- Displaying the paths to a disk
- Setting customized names for DMP nodes
- Administering DMP using the vxdmpadm utility
- Retrieving information about a DMP node
- Displaying consolidated information about the DMP nodes
- Displaying the members of a LUN group
- Displaying paths controlled by a DMP node, controller, enclosure, or array port
- Displaying information about controllers
- Displaying information about enclosures
- Displaying information about array ports
- User-friendly CLI outputs for ALUA arrays
- Displaying information about devices controlled by third-party drivers
- Displaying extended device attributes
- Suppressing or including devices from VxVM control
- Gathering and displaying I/O statistics
- Setting the attributes of the paths to an enclosure
- Displaying the redundancy level of a device or enclosure
- Specifying the minimum number of active paths
- Displaying the I/O policy
- Specifying the I/O policy
- Disabling I/O for paths, controllers, array ports, or DMP nodes
- Enabling I/O for paths, controllers, array ports, or DMP nodes
- Renaming an enclosure
- Configuring the response to I/O failures
- Configuring the I/O throttling mechanism
- Configuring Subpaths Failover Groups (SFG)
- Configuring Low Impact Path Probing (LIPP)
- Displaying recovery option values
- Configuring DMP path restoration policies
- Stopping the DMP path restoration thread
- Displaying the status of the DMP path restoration thread
- Configuring Array Policy Modules
- Administering disks
- About disk management
- Discovering and configuring newly added disk devices
- Partial device discovery
- About discovering disks and dynamically adding disk arrays
- About third-party driver coexistence
- How to administer the Device Discovery Layer
- Listing all the devices including iSCSI
- Listing all the Host Bus Adapters including iSCSI
- Listing the ports configured on a Host Bus Adapter
- Listing the targets configured from a Host Bus Adapter or a port
- Listing the devices configured from a Host Bus Adapter and target
- Getting or setting the iSCSI operational parameters
- Listing all supported disk arrays
- Excluding support for a disk array library
- Re-including support for an excluded disk array library
- Listing excluded disk arrays
- Listing disks claimed in the DISKS category
- Displaying details about an Array Support Library
- Adding unsupported disk arrays to the DISKS category
- Removing disks from the DISKS category
- Foreign devices
- Changing the disk device naming scheme
- Discovering the association between enclosure-based disk names and OS-based disk names
- Dynamic Reconfiguration of devices
- About online Dynamic Reconfiguration
- Reconfiguring a LUN online that is under DMP control using the Dynamic Reconfiguration tool
- Manually reconfiguring a LUN online that is under DMP control
- Overview of manually reconfiguring a LUN
- Manually removing LUNs dynamically from an existing target ID
- Manually adding new LUNs dynamically to a new target ID
- About detecting target ID reuse if the operating system device tree is not cleaned up
- Scanning an operating system device tree after adding or removing LUNs
- Manually cleaning up the operating system device tree after removing LUNs
- Changing the characteristics of a LUN from the array side
- Upgrading the array controller firmware online
- Reformatting NVMe devices manually
- Event monitoring
- Performance monitoring and tuning
- About tuning Dynamic Multi-Pathing (DMP) with templates
- DMP tuning templates
- Example DMP tuning template
- Tuning a DMP host with a configuration attribute template
- Managing the DMP configuration files
- Resetting the DMP tunable parameters and attributes to the default values
- DMP tunable parameters and attributes that are supported for templates
- DMP tunable parameters
- Appendix A. DMP troubleshooting
- Appendix B. Reference
Fabric Monitoring and proactive error detection
DMP takes a proactive role in detecting errors on paths.
The DMP event source daemon vxesd uses the Storage Networking Industry Association (SNIA) HBA API library to receive SAN fabric events from the HBA.
DMP checks devices that are suspect based on the information from the SAN events, even if there is no active I/O. New I/O is directed to healthy paths while DMP verifies the suspect devices.
During startup, vxesd queries the HBA (by way of the SNIA library) to obtain the SAN topology. The vxesd daemon determines the Port World Wide Names (PWWN) that correspond to each of the device paths that are visible to the operating system. After the vxesd daemon obtains the topology, vxesd registers with the HBA for SAN event notification. If LUNs are disconnected from a SAN, the HBA notifies vxesd of the SAN event, specifying the PWWNs that are affected. The vxesd daemon uses this event information and correlates it with the previous topology information to determine which set of device paths have been affected.
The vxesd daemon sends the affected set to the vxconfigd daemon (DDL) so that the device paths can be marked as suspect.
When the path is marked as suspect, DMP does not send new I/O to the path unless it is the last path to the device. In the background, the DMP restore task checks the accessibility of the paths on its next periodic cycle using a SCSI inquiry probe. If the SCSI inquiry fails, DMP disables the path to the affected LUNs, which is also logged in the event log.
If the LUNs are reconnected at a later time, the HBA informs vxesd of the SAN event. When the DMP restore task runs its next test cycle, the disabled paths are checked with the SCSI probe and re-enabled if successful.
Note:
If vxesd receives an HBA LINK UP event, the DMP restore task is restarted and the SCSI probes run immediately, without waiting for the next periodic cycle. When the DMP restore task is restarted, it starts a new periodic cycle. If the disabled paths are not accessible by the time of the first SCSI probe, they are re-tested on the next cycle (300s by default).
The fabric monitor functionality is enabled by default. The value of the dmp_monitor_fabric tunable is persistent across restarts.
To display the current value of the dmp_monitor_fabric tunable, use the following command:
# vxdmpadm gettune dmp_monitor_fabric
To disable the Fabric Monitoring functionality, use the following command:
# vxdmpadm settune dmp_monitor_fabric=off
To enable the Fabric Monitoring functionality, use the following command:
# vxdmpadm settune dmp_monitor_fabric=on