Red Hat Enterprise Linux 5 Administration Unleashed

Using Amanda for Backups 227Setting Up Holding DisksIf holding disks are used, backups are written to the holding disks and then flushed to thetapes, reducing total dump time and the wear on the tape and drive. Dumps from morethan one system can only be done in parallel if a holding disk is used.Holding disks are defined in the amanda.conf file, and one or more holding disks can bedefined. The holding disc on the tape server should be large enough to hold the twolargest backups simultaneously, if possible. The holding disk should also be dedicated tobackups. If a dump is too big for the holding disk, the backup is written directly to tape.TIPIf the backup server crashes or a tape fails during backup, the amflush utility can beused to write data from the holding disk to tape.For example, Listing 10.2 defines the /dumps/DailySet1 as a holding disk directory. Thedirectory must already exist and must be owned by the amanda user because amdump isrun as the amanda user. After creating the directory as root, change the ownership withthe following command:chown amanda.disk /dumps/DailySet1LISTING 10.2Holding Disk Definitionholdingdisk hd1 {comment “first holding disk”directory “/dumps/DailySet1”use -200 Mbchunksize 1Gb}The use parameter specifies the amount of size that can be used by Amanda. If the value is anegative number as in Listing 10.2, Amanda uses all available space except for the value specified.To split large dumps into multiple files, specify the maximum file size for each chunkwith the chunksize parameter, whose value must end in Kb, Mb, Gb, or Tb. The maximumvalue of chunksize is the maximum file size the kernel can allow minus 1 megabyte.Setting Up the Amanda ClientsThis section discusses the configuration of a Red Hat Enterprise Linux Amanda client. Toconfigure clients of a different operating system, refer to www.amanda.org. Each clientmust have the amanda-client RPM package installed. Refer to Chapter 3 for details oninstalling software.10Before configuring the clients, decide the following for each client:. Which files and directories to back up. Whether to use dump or GNU tar to create backups