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Hot Tips for a Cool Disaster Recovery of Linux on System z


Successfully recovering an entire OS in a Linux* on System z* platform, or any Linux or UNIX* environment is never just as simple as an OS reinstall and the quick restore it’s always described to be. A backup typically includes all sorts of files, which if restored will likely crash a running system. A generic “/*” restore (with subdirectories) is pretty much guaranteed to sweep a system right out from under you. Additionally, many files necessary for the OS may not be there in your backup.

There are two ways to do a safe backup and recovery of in a Linux on System z environment:

  • From the outside. You can back up the file systems from z/OS or z/VM. Modern z/Linux file systems are known as compatible, which allows them to be seen by z/OS, thus allowing backup by z/OS tools as well as z/VM tools.
  • From the inside. As a file level backup from inside the “Linux on z” machine.

The first method is quite attractive. It’s efficient and used successfully by many sites; however it requires special hardware support and careful planning. A safe (consistent) backup requires a point-in-time (snapshot) copy be taken of all of the system file systems at the same time (because in-flight data may be cached by the OS). Additionally this type of backup isn’t easily used for a file-level recovery, so typically a file-level backup is done anyway to allow for quick restore of individual files. Consequently, this article will focus on the second method.

A file-level backup that’s to be useful for disaster recovery must contain all of the system files, both the regular files and the special files used by the OS for device data transfer and other system functions. The solution you use should support disaster-recovery backups and that you have enabled any special disaster-recovery options.

An important consideration at backup time is to make note of your volume setup and partitioning, such as by using a sticky note. The important thing is that you know how your disks are partitioned into file systems.

The key to a quick and successful recovery of Linux on System z (besides a good backup), is the ability to boot the OS from a CD or CD image. Most modern Linux systems (SuSE, Red Hat and others) even include a “Rescue” mode. The ability to simply boot into Linux is enough from other OSs. This is the method most likely used to install the Linux OS in the first place, so it’s likely there is someone in your organization who has done this.

Bob Perper is the Chief Open System Network Solutions Architect at INNOVATION Data Processing, where he has lead the work on the development of the company's FDR/UPSTREAM enterprise data protection solutions for the past 10 years.



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