Why backups are performed
Server backups are carried out mainly for the purpose of disaster recovery. Users are therefore responsible for their own data, the accident can not be an excuse for the students to not submit the project, and the data need not be up to date in case of recovery.
When backups are performed
Each backup starts at 1:05 and the day determines the type of backup: In 1st Saturday of the month will start full backups, in other Saturdays will start differential backups against last full backup, and from Monday to Friday every day will start incremental backups against any last backup.
Hidden hazards of differential and incremental backups: For backups, that are not full, the files are stored only if they have newer modification time than last backup. So if someone creates a file with older modification time (e. g. typically extracting archive files *.zip, *.tar, etc.), it is not included in these backups. Another problem may cause the deleted files, which are not identified in differential nor incremental backups. During data restoration for a particular day all files from the last full backup are created and then newer files are updated or added.
What is backuped
All important servers are backuped. From the user aspects, the most important are kazi.fit.vutbr.cz (employee home directories and e-mail), eva.fit.vutbr.cz (student home directories for the FIT and e-mail), aja.fit.vutbr.cz (employee home directories in Windows), fik.fit.vutbr.cz (student home directories for the FIT in Windows), fest.stud.feec.vutbr.cz (student home directories for the FEEC and e-mail), tereza.fit.vutbr.cz (web server), agata.fit.vutbr.cz (database server) and merlin.fit.vutbr.cz (student server).
As of 1. March 2013, there are regularly backuped 28 FIT servers, 5 FEEC servers, and 1 remote server. The total amount of data exceeds 10 TB per one full backup.
How backups are performed
To backup is deployed open-source program Bacula (5.2.12) with GPL licence.
Where backups are stored
Backups are stored on LTO-5 tape drive with 1,5 TB capacity without compression per one tape media. In actual operation, there is often stored about 2 TB per one tape media by hardware compression contained in the tape drives.
Tape drive is located in StorageTek SL 150 tape library with 150 tape slots, automated robot, and barcode reader for quick identification of individual tape media.
Backup speed is highly dependent on a particular server. Limiting factor is not usually connection speed to the backup server (1000 MB/s) nor writing data to tape (140-280 MB/s), but rather the speed of reading data from disks (1-200 MB/s).
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