Configuring backup strategy

In this chapter we'll describe how to configure different types of backup and how to define list of servers to backup.

Configuring styles of backup.

First of all, you need to tell your amanda your dump styles. Mostly for all situations single style is enough, though you can define multiple styles for specific cases

define dumptype default

{

global

estimate calcsize

program "GNUTAR"

dumpcycle 14

comment "root partitions dumped with tar"

compress server fast

index

priority medium

exclude list "amandaexclude"

tape_splitsize 20 Gb

}

Here are the explanations for each option:

global

Means you can use this style to backup your disks. For example, you can define several styles and combine them into final 'global' style. We didn't use that to keep configuration simple.

estimate calcsize

Method to use to estimate data located on your servers. There're 2 most useful possible settings - “calcsize” and “server”. In case of 'calcsize' amanda will run a C++ program on each server to calculate data. It's most accurate way to estimate data but it takes time in case of huge number of files. And second option is 'server', which tells amanda to use estimation from previous runs for this server. If your data is changing so much, amanda may fail to estimate correctly which will cause wrong planning.

program "GNUTAR"

Software to use to archive data. Unless you want to dump your filesystems, gnutar is optimal option.

Dumpcycle 14

How often amanda should perform full backup. We put 14 days (two weeks).

compress server fast

There are two possible options how you want to compress data – on slave servers or backup server. For first method use “client” and for second method use “server”. In our case we had powerful server so we used 'server'. Additionally, you can specify 'best', 'custom', 'fast' to choose compression level.

Index

This option tells amanda to keep database with tape cartridges with list of content on them. Default amanda configuration doesn't have so you must enable it in order to be able to search backup data on tapes.

exclude list "amandaexclude"

On each disk that you will define for your servers, you must put file “amandaexclude”. You need to define list of files or directories that you want to exclude from backup, for example log files. Even if you don't have anything to exclude, you should put at least empty file otherwise backup will fail. For details, see chapter “excluding and splitting backup data”.

priority medium

For some disks you might want to specify different priorities. For example, you can use 'high', 'medium', 'low'. If backup system becomes into degrade status due to some errors ( for example no enough tapes to write), disks with higher priority will be backuped first to make sure that most important data is saved.

tape_splitsize 20 Gb

To reduce fragmentation of your tape space, you can specify maximal size of each data piece wrtten into tape. For example, if you specify 100GB for 200GB tape cartridges, you will definitely fall into high fragmentation because amanda software will have to find a tape cartridge with 100GB unused space. If you specify very small chunk's size, performance of writing to tape cartridges will degrade.

Configuring slave servers

On this step we will show how to make list of slave servers, and their disks that you'd like to backup. There's a file called disklist located in your configuration directory. In our case it was /usr/local/etc/amanda/DailySet1/disklist.
This file has a list of top directories on each server that you want to backup. For example, here's an example:

server1.domain.com /
{
default
}

server1.domain.com /boot
{

server1.domain.com /var
{
default
}

server1.domain.com /usr
{
default
}

server1.domain.com /home
{
default
}

You might ask “Why did you define many directories instead of putting single item with root directory '/' ? “. When amanda runs tar software, it specifies that tar should stay on single file system so that neither symlinks nor NFS mounts nor any other mounting manipulations causes double backup data. On our servers we use dedicated partitions for /boot, /home/, /usr, and /var. so we had to specify all partitions we had. If you home is very huge, you should split it into sub-backups. Refer to the chapter “excluding and splitting backup data”.

To define backup style, open /usr/local/etc/amanda/DailySet1/amanda.conf and configure the following definition:

define dumptype root-tar {
        global
        estimate calcsize
        program "GNUTAR"        
        dumpcycle 14
        comment "root partitions dumped with tar"
}