Cosc 4750

Backups

Why Backup?

• In case of failure

• In case of loss of files– User and system files

• Because you will regret it, if you don’t.– DUMB = Disasters Usually Motive Backups

How to backup.

• You want to pick a reasonable interval to backup– Every night, once a week, once a month?

• What to backup?– user files, system configuration?

• Where to store you backups?– on-site, off-site, next to the computer?

• When do you backup?– During the day, night ?

• Always assume the worst case.– The computer caught fire and burned down the server

room and the building.• What should you have backed up? Where should the backups

have been stored?

• In a perfect world, everyone would backup everything daily, onto a single tape (stored in the next state in a fire proof vault).– Rarely possible or even needed.

What to use?

• Many use a tape device– 8MM, 4MM, DLT, AIT, LTO, etc.

– LTO-6 is 2.5TB/6.25TB compress @1.4TB/Hr• About $2,300 for the drive, each tape about $57 (as of Feb 2015)

• Floppy disks/Zip disks?• CD, DVD ?• Removable hard drives?• RAID, with backups as well.• A lot depends on need and cost.

Full and Incremental backups

• Full– The entire area you want to backup. All the

files are stored on “tape”

• Incremental– Only those files that have changed are written

off to “tape”, since the last full backup– There can be many incremental backups

between full backups.

Hardware backups

• RAID devices.– Could choose to use RAID 1 (disk mirroring)– RAID 5, a lost disk, the "volume" can be

recreated.• Lessens the change of disk failure and system lost

– RAID does not prevent lost of data by users deleting files.

– You would still want to perform a full backups every so often.

Backup products

• By default dump and restore are installed on UNIX systems.– dump will write a filesystem to a backup device– restore will restore a file/filesystem to the hard

drive

• You can use tar– Will “tar” files off to a backup device or to a

file that can be copied somewhere else.

• Can use dd– Normally used to copy an entire filesystem

from one hard to another or tape.– Used to “mirror” drives.

• Amanda (Advanced Maryland Automatic Network Disk Archiver)– Use a single large-capacity tape drive on a

server to backup files from multiple computers over the network.

Commercial Software

• There is a lot of it. The book lists a couple and a web site for the rest.

• Computer Science used to use a program called bru for UNIX backups.– Command line and GUI interface.– Can script the backups

Backup storage

• Backups by their nature, break all security and permissions.– The entire tape is readable by whom ever has

the tape.– Security and safety of the tape must be dealt

with as well.– Tapes are also vulnerable to electric magnetic

fields (such as the seat warmers in most cars)

What to backup?

• Systems files and users files, but– Do need to backup the kernel? Or just configuration

files? If so, which ones?– Do you really need to backup users MP3 collections?

Their .jpg collections?, etc.– What about other stuff, such as commercial software,

where you have the install media?

• Most products allow you be selective about what you backup, with a Don’t backup list, (usually wildcard list).

Users Backup

• Users may want backup their stuff as well.– "personal" backups.

• rsync is program that can maintain copies of directories over the network.

– What kind of rules are setup?• tapes, when, etc.

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