1 itec 400 Backups George Vaughan Franklin University

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itec 400Backups

George Vaughan

Franklin University

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Topics

• Determining Backup Needs

• Backup Strategies

• Data Verification

• Storage

• Backup Media

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Determining Backup Needs

• Your Valuables (Data)– research data– billing, tax records– customer data

• Your Insurance (Backups/Archives)– cost (money, interference with operations)– quality of insurance policy (backup process)– speed of recovery– type of disasters covered

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Determining Backup Needs

• Can you tolerate the loss of everything?

• Can you tolerate the loss of some filesystems or files? which ones?

• How often is this critical data changing?

• How long can you wait before it is restored?

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Determining Backup Needs

• How old can the restored version be (hours, days, weeks)?

• How much can you afford to spend on a backup strategy?

• Does your system need to be available 24x7?

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Backup Strategies

• Different Strategies may be applied to different filesystems.

• 2 Types of backups– Full Backup– Incremental Backup

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Backup Strategies

• Full Backup– Backup everything– Can take a long time– Can consume a lot of backup media– Simplest to restore from

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Backup Strategies

• Incremental: – only backup files that changed since some

point in time.– Faster Backups– Less consumption of backup media– More complicated restore process– Still need to do full backup every once in a

while

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Multi-level backup

• A popular strategy: multi-level backup– Level 0: Full Backup.– Level 1: Incremental backup since last level 0

backup.– Level 2: Incremental backup since last level 1

backup.

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Multi-level backup

Sun Mon Tue Wed Thur Fri Sat

1

0

2

13

24

25

26

27

8 9

110

211

212

213

214

15 16

117

218

219

220

221

22 23

124

225

226

227

228

• Level 0: First Sunday of Month• Level 1: Every Monday• Level 2: Every Tuesday through Friday• If I accidentally deleted my directory on the 25th, which backups do I need?

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Data Verification

• You never know how good your backups are until you need to restore.

• You can’t wait till disaster hits only to find that your tape units were never working.

• Need to periodically check/verify backups– against original files– on alternative machines– for backup media degradation

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Storage

• Where should you store your backups?

• Maybe store level 1 and level 2 in an alternate location?

• What about archived data?

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Organization of Backups

• Labels– Color Coded– Printed

• Dedicated Shelf Location– By Day of Week?– By Week of Month?

• 3rd Party Software– Stored separately?

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Backup MediaType Capacity (GB) Media Price

($)($)/GB Drive Price

($)

Mammoth Tape 60.00 45.00 0.75 3700

8mm Tape 7.00 6.00 0.86 1200

AIT Tape 100.00 105.00 1.05 3900

Hard Disk 100.00 120.00 1.20 120

CD-R 0.70 0.85 1.21 150

CD-RW 0.64 1.00 1.56 150

DVD-R 4.70 8.00 1.70 400

DVD-RW 4.70 8.00 1.70 400

Zip Disk 0.25 12.00 48.00 140

Zip Disk 0.10 5.00 50.00 70

Jazz Disk 2.00 100.00 50.00 340

Jazz Disk 1.00 80.00 80.00 300

Floppy 0.00 0.25 178.57 10

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Backup Tools

• Tools/Commands to facilitate backups:– tar– cpio– dump/restore– amanda

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tar

• tar - tape archive utility– a tar file is a file that contains other files and

directories, plus information about them, such as their file name, owner, timestamps, and access permissions.

– The archive can be another file on the disk, a magnetic tape, or a pipe. used to store and extract files from ‘tarfile’

– commonly used to for creating a tarfile on disk

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Example: Creating a tar File

• Solaris example: create a compressed tarfile containing the directory ‘myDir’:– First, create the tar file from the directory

“myDir”:tar cf myDir.tar myDir

-Next, compress the tar file, for easier distribution and/or storagegzip myDir.tar

-Finally we end up with a compressed tar file named, “myDir.tar.gz”

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Example: Unpacking a tar File

• Solaris example: create a directory from a compressed tarfile named ‘myDir.tar.gz’:– First, uncompress the the tar file:

gunzip myDir.tar.gz

-Next, untar the file. This will result in a directory named myDirtar xf myDir.tar

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cpio

• cpio - copy in and out of archive– copies files into or out of a cpio or tar archive– cpio has three operating modes:

• copy-out - copies files out to archive• copy-in - copies files in from archive• copy-pass - copies files from one directory tree to

another without creating intermediate archive

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Example: Creating a cpio File

• Solaris example: create a compressed cpio file containing the directory ‘myDir’:– First, create the cpio file from the directory

“myDir”:find myDir | cpio -o > myDir.cpio

-Next, compress the cpio file, for easier distribution and/or storagegzip myDir.cpio

-Finally we end up with a compressed cpio file named, “myDir.cpio.gz”

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Example: Unpacking a cpio File

• Solaris example: create a directory from a compressed cpio file named ‘myDir.cpio.gz’:– First, uncompress the cpio file:

gunzip myDir.cpio.gz

-Next, unpack the cpio file. This will result in a directory named myDircpio -imd ‘myDir’ < myDir.cpio

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dump/restore

• The dump and restore commands are used collectively

• More sophisticated than tar, cpio

• Supports multi-level backups

• Records backup history in /etc/dumpdates

• restore supports interactive mode

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Example of dump/restore

0009: dump -0 -u -f /backup/home_0 /home

0010: DUMP: Date of this level 0 dump: Mon Mar 10 23:08:54 2003

0011: DUMP: Dumping /dev/hdb2 (/home) to /backup/home_0

0025: DUMP: finished in 39 seconds, throughput 6498 kBytes/sec

0026: DUMP: Date of this level 0 dump: Mon Mar 10 23:08:54 2003

0027: DUMP: Date this dump completed: Mon Mar 10 23:10:48 2003

0028: DUMP: Average transfer rate: 2283 kB/s

0029: DUMP: DUMP IS DONE

• Line 9: perform level 0 (full) backup of /home filesystem and store in file /backup/home_0

• Lines 10-29: output of dump

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Example of dump/restore0031: # cat /etc/dumpdates0032: /dev/hdb2 0 Mon Mar 10 23:08:54

2003

0034: # dump -1 -u -f /backup/home_1 /home

0035: DUMP: Date of this level 1 dump: Mon Mar 10 23:14:32 2003

0060: rm -rf dummy

• Lines 31-32: Look at contents of dumpdates

• Lines 34-35: Perform level 1 (incremental) backup

• Line 60: The act of much regret…

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Example of dump/restore0062: # cd /home0063: 0064: # restore -i -f /backup/home_00065: restore > ls0066: .:0067: dummy/ dummy1/

gvaughan/ johnsonm/lost+found/

0068: 0069: restore > add dummy0070: restore > extract0071: You have not read any tapes yet.0072: Unless you know which volume your

file(s) are on you should start0073: with the last volume and work

towards the first.0074: Specify next volume #: 10075: set owner/mode for '.'? [yn] n0076: restore > quit

• Line 62: cd to filesystem

• Line 64: restore for level 0 backup

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Example of backup/restore

0082: # restore -i -f /backup/home_1

0102: # cat /etc/dumpdates

0103: /dev/hdb2 0 Mon Mar 10 23:08:54 2003

0104: /dev/hdb2 1 Mon Mar 10 23:14:32 2003

• Line 82: Complete restore from level_1 backup.

• Lines 102-104: Look at contents of /etc/dumpdates

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Amanda

• amanda - Advanced Maryland Automatic Network Disk Archiver

• Developed at University of Maryland

• Client/Server model

• Multiple clients can be backed up onto a single backup server.

• Uses a combination of full and incremental backups.