Introducing the VERITAS Volume Manager
The VERITAS Volume Manager is an alternative Volume Management product for HP-UX that includes mirroring features. It offers many capabilities that are not available with the LVM and MirrorDisk/UX products today.
- The VERITAS Volume Manager can coexist with LVM. Users can decide which volumes they want managed by each volume manager. For users who want to migrate LVM volume groups to VxVM disk groups, a conversion utility is included. This utility, vxvmconvert, is described in detail in Converting LVM to VxVM.
- With HP-UX 11i Version 2, the VERITAS Volume Manager is available for installation with the HP-UX 11i Version 2 Application Software. See the Release Notes for details of features supported in this release.
- With HP-UX 11i Version 2, the VERITAS Volume Manager is the default volume manager and can be used instead of LVM to manage the root disk. Basic volume management capabilities are included in the operating system.
- The VERITAS Volume Manager is integrated with HP MC/ServiceGuard and ServiceGuard OPS Edition for High Availability, but requires a specific version of the ServiceGuard products. Refer to the Release Notes for details about the required version number, as well as the availability of specific features in your release.
Notable Features of VxVM
The VERITAS Volume Manager provides many features, some of which are not available with LVM or MirrorDisk/UX. Notable VxVM features are described in the list below. See the Release Notes for a more detailed list of features available in each VERITAS Volume Manager product. See the other VERITAS Volume Manager documents (listed under Preface) for more details about using these features.
VERITAS Volume Manager includes the following features:
- Concatenation, the combining of discontiguous disk regions into virtual devices.
- Spanning, concatenation across different physical media.
- Striping, distribution of storage mappings for a virtual device so that multi-threaded accesses tend to cause even use of all physical media.
- The VERITAS Enterprise Administrator (VEA), which is a JAVA-based GUI for VxVM.
- Dynamic Multipathing (DMP) for active-passive devices, such as FC60. DMP provides higher availability to data on disks with multiple host-to-device pathways by providing a disk/device path failover mechanism. In the event of a loss of one connection to a disk, the system continues to access the data over the other available connections to the disk.
- Free Space Management, providing simple goal-based allocation of storage.
- Task Monitor, which tracks the progress of system recovery by monitoring task creation, maintenance, and completion. The Task Monitor allows you to pause, resume, and stop as desired to adjust the impact on system performance.
- Dynamic Multipathing (DMP) for active-active devices, such as HP Surestore Disk Array xp256, HP Surestore Disk System FC10 and other disk devices. DMP provides higher availability to data on disks with multiple host-to-device pathways by providing a disk/device path failover mechanism. In the event of a loss of one connection to a disk, the system continues to access the data over the other available connections to the disk. DMP also provides in some cases, improved I/O performance from disks with multiple concurrently available pathways by balancing the I/O load uniformly across multiple I/O paths to the disk device. LVM supports path failover but does not support I/O balancing. DMP support may be used with devices that show improved performance when I/O is balanced across the multiple paths such as xp256, EMC Symmetrix disk array, and other OEM array devices.
- Multiple mirroring with up to 32 mirror copies of a volume's address space.
- Mirrored stripes (RAID-0 + RAID-1) and striped mirrors (RAID-1 + RAID-0) combine the benefits of striping to improve performance by spreading data across multiple disks, and mirroring to provide redundancy of data. Striped mirror volumes are more tolerant of disk failure and have a shorter recovery time than mirrored stripe volumes. Refer to the VERITAS Volume Manager 3.5 Administrator's Guide for more detailed information on these layouts.
- Hot-relocation, which allows a system to react automatically to I/O failures on redundant (mirrored or RAID-5) VxVM objects, restoring redundancy and access to those objects without administrative intervention. VxVM detects I/O failures on objects and relocates the affected subdisks. The vxunreloc utility can be used to restore the system to the same configuration that existed before the disk failure.
- RAID-5, which provides data redundancy by using parity, at a lower storage cost than mirroring. RAID-5 provides data redundancy by using parity. Parity is a calculated value used to reconstruct data after a failure. While data is being written to a RAID-5 volume, parity is calculated by doing an exclusive OR (XOR) procedure on the data. The resulting parity is then written in an interleaved fashion to the RAID-5 array established by the volume. If a portion of a RAID-5 volume fails, the data that was on that portion of the failed volume can be recreated from the remaining data and parity information.
- Online Data Migration, which allows for regions of storage on physical media to be dynamically moved to other physical devices.
- Online Relayout or Dynamic Restriping, the ability to change logical data configuration while online, for example, to change RAID-5 to a mirrored layout or to change a stripe unit size. The volume data remains available during the relayout.
- Improved RAID-5 subdisk, using layered volume technology where the RAID-5 subdisk move operation leaves the old subdisk in place while the new one is being synchronized, thus maintaining redundancy and resiliency to failures during the move.
Note
For more information on LVM, refer to HP-UX Managing Systems and Workgroups, and LVM manual pages in HP-UX Reference Volumes 2, 3, and 5. For information on VxVM commands, refer to the VERITAS Volume Manager documentation.
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