Chapter SIX. Disks and Volumes: LVM

     

Chapter Syllabus

6.1 LVM Striping (RAID 0)

6.2 LVM Mirroring (RAID 1)

6.3 Alternate PV Links

6.4 Exporting and Importing Volume Groups

6.5 Forward Compatibility with Newer, Larger Capacity Disk Drives

In Chapter 5, we discussed the basics of managing disks, including establishing which disks are currently in use by other subsystems. In this chapter, we concentrate on looking at Logical Volume Manager. LVM is the most used disk-management software on HP-UX. We look at advanced features such as striping and mirroring. Our discussions assume a good working knowledge of LVM.

Logical Volume Manager (LVM) is still the most common disk management software on HP-UX. I think this is due to four main factors:

  1. The large installed base using the software already.

  2. The inclusion of additional functionality, i.e., MirrorDisk/UX as a no-cost option with the 11i Mission Critical Operating Environment.

  3. Increased functionality such as RAID 5 is probably best achieved via a hardware solution, i.e., a disk array.

  4. VxVM additional functionality, i.e., mirroring, striping, Dynamic Multi Pathing, comes at an additional cost.

LVM has been around since HP-UX 9.0 and is a stable product that has seen its way into the Linux arena as well. It can achieve most things a disk administrator wants. It is commonly argued that the things that LVM cannot achieve, the biggest being RAID 5, are solutions that are best not performed by the operating system itself because it is too costly as far as processing time and should, therefore, be implemented in hardware. There are RAID controllers and disk arrays that can achieve these solutions at diminishing costs. In short, LVM looks to be with us for the next few years at least. For administrators who have been around HP-UX for some time, this is good news because we are comfortable with LVM and have seen it evolve into the product it is now. We look at some of the advanced configurations that LVM finds itself in. These include mirroring, striping (extent and kilobyte striping), rootability , and recovery after a disk failure.

Please note that although LVM supports RAID 0, 1, 0/1 (with Distributed Volumes), such a solution would be regarded as software RAID . If you are implementing a RAID solution, it is always best to implement RAID using a hardware RAID array. Software RAID solutions are expensive in terms of server CPU cycles and should be used only where no other solution is possible.



HP-UX CSE(c) Official Study Guide and Desk Reference
HP-UX CSE(c) Official Study Guide and Desk Reference
ISBN: N/A
EAN: N/A
Year: 2006
Pages: 434

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