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
Example of applying load balancing in a SAN
This example describes how to use Dynamic Multi-Pathing (DMP) to configure load balancing in a SAN environment where there are multiple primary paths to an Active/Passive device through several SAN switches.
As shown in this sample output from the vxdisk list command, the device sdm has eight primary paths:
# vxdisk list sdq Device: sdq . . . numpaths: 8 sdj state=enabled type=primary sdk state=enabled type=primary sdl state=enabled type=primary sdm state=enabled type=primary sdn state=enabled type=primary sdo state=enabled type=primary sdp state=enabled type=primary sdq state=enabled type=primary
In addition, the device is in the enclosure ENC0, belongs to the disk group mydg, and contains a simple concatenated volume myvol1.
The first step is to enable the gathering of DMP statistics:
# vxdmpadm iostat start
Next, use the dd command to apply an input workload from the volume:
# dd if=/dev/vx/rdsk/mydg/myvol1 of=/dev/null &
By running the vxdmpadm iostat command to display the DMP statistics for the device, it can be seen that all I/O is being directed to one path, sdq:
# vxdmpadm iostat show dmpnodename=sdq interval=5 count=2 . . . cpu usage = 11294us per cpu memory = 32768b OPERATIONS KBYTES AVG TIME(ms) PATHNAME READS WRITES READS WRITES READS WRITES sdj 0 0 0 0 0.00 0.00 sdk 0 0 0 0 0.00 0.00 sdl 0 0 0 0 0.00 0.00 sdm 0 0 0 0 0.00 0.00 sdn 0 0 0 0 0.00 0.00 sdo 0 0 0 0 0.00 0.00 sdp 0 0 0 0 0.00 0.00 sdq 10986 0 5493 0 0.41 0.00
The vxdmpadm command is used to display the I/O policy for the enclosure that contains the device:
# vxdmpadm getattr enclosure ENC0 iopolicy ENCLR_NAME DEFAULT CURRENT ============================================ ENC0 MinimumQ Single-Active
This shows that the policy for the enclosure is set to singleactive, which explains why all the I/O is taking place on one path.
To balance the I/O load across the multiple primary paths, the policy is set to round-robin as shown here:
# vxdmpadm setattr enclosure ENC0 iopolicy=round-robin # vxdmpadm getattr enclosure ENC0 iopolicy ENCLR_NAME DEFAULT CURRENT ============================================ ENC0 MinimumQ Round-Robin
The DMP statistics are now reset:
# vxdmpadm iostat reset
With the workload still running, the effect of changing the I/O policy to balance the load across the primary paths can now be seen.
# vxdmpadm iostat show dmpnodename=sdq interval=5 count=2 . . . cpu usage = 14403us per cpu memory = 32768b OPERATIONS KBYTES AVG TIME(ms) PATHNAME READS WRITES READS WRITES READS WRITES sdj 2041 0 1021 0 0.39 0.00 sdk 1894 0 947 0 0.39 0.00 sdl 2008 0 1004 0 0.39 0.00 sdm 2054 0 1027 0 0.40 0.00 sdn 2171 0 1086 0 0.39 0.00 sdo 2095 0 1048 0 0.39 0.00 sdp 2073 0 1036 0 0.39 0.00 sdq 2042 0 1021 0 0.39 0.00
The enclosure can be returned to the single active I/O policy by entering the following command:
# vxdmpadm setattr enclosure ENC0 iopolicy=singleactive