This topic discusses Linux® backup and recovery.
Linux-centric backup is inherently file oriented in nature because Linux backup utilities operate at a file level. It is very difficult to back up an entire Linux drive as a single entity using Linux backup utilities. The only way to save a complete copy of a disk volume using Linux is to buy a third-party imaging product. These products require special skills to use, and are not supported for use with integrated Linux servers.
It should be noted that when we discuss Linux file-level backup and the applications that can be used to perform this task, we are really talking about Linux flat files, that is, non-database files. In i5/OS™, we usually do not draw such a distinction because we use the same backup tools to save both database and non-database files. In Linux, however, you would usually back up database files using a backup application that is specific to the installed database. Therefore, when we discuss file-level backup in this section it is in the context of flat, or non-database, files.
There are other differences between an i5/OS and Linux backup. When performing an i5/OS backup, we usually put the partition to restricted state and save objects direct to tape. While the data can be compressed, the objects are written sequentially on the tape and not saved to a single container (archive in Linux terms). When backing up to tape, this is the most logical and efficient way to perform a save. In the Linux world, however, a backup usually means saving files to a single archive file on disk. The archive file can then either be copied to another Linux server in the network for safekeeping, or dumped to tape.
When we discuss backup we usually assume that we are backing up to tape. However, we can also back up to disk. Backing up to disk is usually an intermediate step before saving to tape in a staged backup. Ultimately we must back up to tape, or to disk on another system to guard against a complete loss of the primary system. While backup to tape is fairly straightforward, there are applications and techniques that can also be used to save data to disk on remote systems so that files can be quickly recovered in the event of a data loss.
Although Linux documentation might talk about “disaster recovery” backup, we need to draw a distinction between the disaster recovery backup capability provided by i5/OS for an integrated Linux server, and disaster recovery in the context of a Linux backup application. From the Linux point of view, a disaster recovery backup is a backup of all files on a disk volume or volumes versus backing up selected files. However, Linux backup applications still save at a file level, and you can still restore individual files from a Linux “disaster recovery” backup. In contrast, an i5/OS storage space backup saves a complete image of a Linux drive as a single entity, and you cannot directly restore individual files from it. You can restore the storage space to a new name and link it to the same server, then copy the needed files from it. However, i5/OS storage space backup is very fast, and can provide additional functions not readily available with a Linux "disaster recovery" backup, such as the ability to quickly restore a complete copy of the system drive. In the context of this information, we regard all Linux backup operations as file-level backups.
Note that the tape drive must be varied off in the hosting i5/OS partition. Tape devices show up under the /dev directory, for example, /dev/st0 or /dev/st1.
Using a Linux application to perform file-level backups can be difficult to incorporate into an unattended backup from the i5/OS side. This is because Linux cannot share a tape cartridge formatted for use by i5/OS.
There are some good reasons why you might want to use an iSeries tape drive in preference to an Integrated xSeries® Server or xSeries-attached tape drive. iSeries tape drives tend to be very fast, reliable, robust and high capacity; and it can be possible to consolidate a number of tape drives in your organization down to one or two iSeries devices. If you have multiple integrated Linux servers in the same i5/OS partition, they can all access the same tape drive (although not at the same time). Therefore, you might only need one iSeries tape drive to back up all your Linux servers.
You can find more information about Linux backup strategies and automating the backup process, along with general information about backup and restore, at the following Web site:
