| Chapter Syllabus 7.1 Introducing VxVM 7.2 VxVM Striping (RAID 0) 7.3 VxVM Mirroring (RAID 1) 7.4 VxVM Striping and Mirroring (RAID 0/1 and 1/0) 7.5 Faster Mirror Resynchronization after a System Crash 7.6 VxVM RAID 5 7.7 Recovering from a Failed Disk 7.8 Using Spare Disks 7.9 VxVM Snapshots 7.10 VxVM Rootability 7.11 Other VxVM Tasks VxVM started its life with HP-UX with VxVM version 3.0 for HP-UX 11.0. VxVM has increased its popularity with support for VxVM version 3.5 for HP-X 11i. When it first appeared on the HP-UX scene, it was greeted with a mixed reception . Some people wondered why HP was abandoning LVM in favor of a third-party product. The truth is that HP isn't abandoning LVM; it's just that we, the customers, are demanding more from our operating systems. This insatiable appetite extends to the choice of disk management software. Many of us have to accept that there are other versions of UNIX in the marketplace . Some of them are actually doing quite well. The misguided among us have even paid good money for some of these machines. In what seems like a completely reckless venture, we want our other versions of UNIX to coexist alongside HP-UX. We even want disk management software that is available on both platforms in order for data to be available to both operating systems. What a bizarre idea. Or is it? In fact, we have to accept that coexisting with other operating systems is the way forward. We may even have to coexist with those rowdy young upstarts from Seattle. This is where products like VxVM come to the fore. Being available on different operating systems is a big attraction to some customers. This has seen the continued growth of VxVM in the HP-UX arena. Is it better than LVM? I wouldn't use the word better . I would say it's an alternative; that's all, an alternative to LVM. Yes, it does have more capabilities than LVM. Yes, it can be seen to perform better than LVM (using some of its advanced features). But these advantages come at a financial cost; the advanced features available for VxVM require the purchase of an additional software license. Some would say that the financial cost is negligible when considered in the context of a complete heterogeneous solution, but it is still a cost and needs to be accounted for, understood , and accepted. For some customers, there is the feeling that using a third-party product at the heart of an operating system is in some ways anathema; they want only HP software running HP-UX; they point out that until recently VxVM was not rootable on PA-RISC ( rootable = the ability to host the root and boot filesystems). All these feelings are valid. Whatever viewpoint you have on this, you must acknowledge that VxVM needs to be considered on its own merits. We look at the features that LVM offers, but in the context of VxVM. We also look at features of VxVM that LVM does not offer. Please note that although VxVM supports RAID 0, 1, 0/1, 1/0, and 5, 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. |
