Storage Foundation 7.4.1 Administrator's Guide - Linux
- Section I. Introducing Storage Foundation
- Overview of Storage Foundation
- How Dynamic Multi-Pathing works
- How Veritas Volume Manager works
- How Veritas Volume Manager works with the operating system
- How Veritas Volume Manager handles storage management
- Volume layouts in Veritas Volume Manager
- Online relayout
- Volume resynchronization
- Dirty region logging
- Volume snapshots
- FastResync
- How VxVM handles hardware clones or snapshots
- Volume encryption
- How Veritas File System works
- Section II. Provisioning storage
- Provisioning new storage
- Advanced allocation methods for configuring storage
- Customizing allocation behavior
- Using rules to make volume allocation more efficient
- Understanding persistent attributes
- Customizing disk classes for allocation
- Specifying allocation constraints for vxassist operations with the use clause and the require clause
- Creating volumes of a specific layout
- Customizing allocation behavior
- Creating and mounting VxFS file systems
- Creating a VxFS file system
- Mounting a VxFS file system
- tmplog mount option
- ioerror mount option
- largefiles and nolargefiles mount options
- Resizing a file system
- Monitoring free space
- Extent attributes
- Section III. Administering multi-pathing with DMP
- Administering Dynamic Multi-Pathing
- Discovering and configuring newly added disk devices
- About discovering disks and dynamically adding disk arrays
- How to administer the Device Discovery Layer
- Administering DMP using the vxdmpadm utility
- Gathering and displaying I/O statistics
- Specifying the I/O policy
- Discovering and configuring newly added disk devices
- Dynamic Reconfiguration of devices
- Reconfiguring a LUN online that is under DMP control using the Dynamic Reconfiguration tool
- Manually reconfiguring a LUN online that is under DMP control
- Managing devices
- Displaying disk information
- Changing the disk device naming scheme
- Adding and removing disks
- Event monitoring
- Administering Dynamic Multi-Pathing
- Section IV. Administering Storage Foundation
- 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
- Administering sites and remote mirrors
- Section V. Optimizing I/O performance
- Veritas File System I/O
- Veritas Volume Manager I/O
- Managing application I/O workloads using maximum IOPS settings
- Section VI. Using Point-in-time copies
- Understanding point-in-time copy methods
- When to use point-in-time copies
- About Storage Foundation point-in-time copy technologies
- Volume-level snapshots
- Storage Checkpoints
- About FileSnaps
- About snapshot file systems
- Administering volume snapshots
- Traditional third-mirror break-off snapshots
- Full-sized instant snapshots
- Creating instant snapshots
- Adding an instant snap DCO and DCO volume
- Controlling instant snapshot synchronization
- Creating instant snapshots
- Cascaded snapshots
- Adding a version 0 DCO and DCO volume
- Administering Storage Checkpoints
- Storage Checkpoint administration
- Administering FileSnaps
- Administering snapshot file systems
- Understanding point-in-time copy methods
- Section VII. Optimizing storage with Storage Foundation
- Understanding storage optimization solutions in Storage Foundation
- Migrating data from thick storage to thin storage
- Maintaining Thin Storage with Thin Reclamation
- Reclamation of storage on thin reclamation arrays
- Identifying thin and thin reclamation LUNs
- Veritas InfoScale 4k sector device support solution
- Section VIII. Maximizing storage utilization
- Understanding storage tiering with SmartTier
- Creating and administering volume sets
- Multi-volume file systems
- Features implemented using multi-volume file system (MVFS) support
- Adding a volume to and removing a volume from a multi-volume file system
- Volume encapsulation
- Load balancing
- Administering SmartTier
- About SmartTier
- Placement classes
- Administering placement policies
- File placement policy rules
- Multiple criteria in file placement policy rule statements
- Using SmartTier with solid state disks
- Sub-file relocation
- Administering hot-relocation
- How hot-relocation works
- Moving relocated subdisks
- Deduplicating data
- Compressing files
- About compressing files
- Use cases for compressing files
- Section IX. Administering storage
- Managing volumes and disk groups
- Rules for determining the default disk group
- Moving volumes or disks
- Monitoring and controlling tasks
- Performing online relayout
- Adding a mirror to a volume
- Managing disk groups
- Disk group versions
- Displaying disk group information
- Importing a disk group
- Moving disk groups between systems
- Importing a disk group containing hardware cloned disks
- Handling conflicting configuration copies
- Destroying a disk group
- Backing up and restoring disk group configuration data
- Managing plexes and subdisks
- Decommissioning storage
- Rootability
- Encapsulating a disk
- Rootability
- Sample supported root disk layouts for encapsulation
- Encapsulating and mirroring the root disk
- Administering an encapsulated boot disk
- Quotas
- Using Veritas File System quotas
- File Change Log
- Managing volumes and disk groups
- Section X. Reference
- Appendix A. Reverse path name lookup
- Appendix B. Tunable parameters
- Tuning the VxFS file system
- Methods to change Dynamic Multi-Pathing tunable parameters
- Tunable parameters for VxVM
- Methods to change Veritas Volume Manager tunable parameters
- Appendix C. Command reference
Changing the read policy for mirrored volumes
For a mirrored volume, Veritas Volume Manager (VxVM) uses the read policy to determine which data plex in the volume to use for reads. By default, VxVM chooses a plex using the following criteria, in order:
Site
Plexes on the same site are chosen over plexes on another site.
Connectivity
Locally connected plexes are chosen over remotely connected plexes. This criterion applies for shared disk groups.
Media type
SSD devices are chosen over HDDs.
Layout
Striped plexes are chosen over other layouts
To customize the read policy, you can choose one of the following VxVM read policies:
Uses a particular named plex to satisfy read requests. Specify one preferred plex when you set the prefer policy. If a read request cannot be satisfied by the preferred plex, VxVM applies the plex order in the select policy. | |
Distributes the non-sequential read operations in "round-robin" fashion across all of the available plexes. For example, given three plexes, VxVM switches between each of the three plexes, so that each plex receives one third of the read requests. Sequential read operations access only one plex. This approach takes advantage of the drive or controller read-ahead caching policies. | |
Chooses a plex based on the characteristics of the plex. The select policy is the default read policy, unless site consistency is enabled. If sites are configured, VxVM internally switches to the siteread policy. The select policy chooses a plex in the following order:
If VxVM cannot find a plex with the above characteristics, VxVM uses the round policy. | |
Reads preferentially from plexes at the locally defined site. This method is the default policy for volumes in disk groups where site consistency is enabled. The siteread policy chooses a plex in the following order:
If VxVM cannot find a plex with the above characteristics, VxVM refers to the plex order in the select policy. | |
Divides the read requests and distributes them across all the available plexes. |
Note:
You cannot set the read policy on a RAID-5 volume.
To set the read policy to round, use the following command:
# vxvol [-g diskgroup] rdpol round volume
For example, to set the read policy for the volume vol01 in disk group mydg to round-robin, use the following command:
# vxvol -g mydg rdpol round vol01
To set the read policy to prefer, use the following command:
# vxvol [-g diskgroup] rdpol prefer volume preferred_plex
For example, to set the policy for vol01 to read preferentially from the plex vol01-02, use the following command:
# vxvol -g mydg rdpol prefer vol01 vol01-02
To set the read policy to select, use the following command:
# vxvol [-g diskgroup] rdpol select volume