Chapter 10

CT 320: Network and System Administra8on Fall 2014*

Dr. Indrajit Ray Email: [email protected]

Department of Computer Science

Colorado State University Fort Collins, CO 80528, USA

Dr. Indrajit Ray, Computer Science Department CT 320 Network and Systems Administra8on, Fall 2014

* Thanks to Dr. James Walden, NKU and Russ Wakeeld, CSU for contents of these slides

Backups


Topics


1. Backup policies and capacity planning. 2. Types of backups. 3. Backup media 4. Automa8on 5. Backup security.

Why Backups?


1. Accidental dele8ons. 2. Hardware failures. 3. Data corrup8on. 4. Security incidents.

Backup Types

Full backup Complete copy of all les from a par8cular 8me. Backup: slow, requires high capacity. Restore: fast, simple.

Incremental backup Storage of changed les since last backup. Backup: fast, may store mul8ple per tape. Restore: slow, complex (requires mul8ple tapes)


Backup Policies

Backup requirements for organiza8on. Explains reasons for backups. Explains what backups are. Indicates which data is backed up. Indicates frequency of backups. Provides backup SLA. Denes legal data reten8on requirements.


SLA Parameters

File restore 8me and granularity How long to restore a le? Snapshots, tapes. Daily to monthly granularity, depending on age.

Disk failure restore 8me How long to restore the disk? Hours, days. How much data will be lost? Last 24 hours.

Data reten8on legal policies E-mail stored only for 30-days, for example.


Backup Schedule

Determined by Policy and SLA. Schedule provides following informa8on: Which servers, par88ons backed up? How oben are full backups performed? How oben are incrementals performed?

Schedule determines capacity needs.


Capacity Planning: Space

Par88on: 40GB Full backup every week. Daily incremental backups. 50% full now, grows 2GB per day

Tape capacity needed Day 1: 40GB Day 2: 2GB Day 7: 12GB Day 8: 40GB


Capacity Planning: Time

Fileserver: 4TB Full backup must nish overnight (8 hours) Tape drive: 40MB/s = 144 GB/hr = 1.15TB/night Need 4 tape drives running simultaneously. Addi8onal concerns: Network performance between le & backup servers. Does any capacity need to be reserved for restores? Actual performance vs. manufacturer specs.


Capacity Planning: Media

How much media do you need? Determined by policy and schedule. How long are full backups kept? How oben are incrementals recycled? How oben are tapes moved o-site?


Choosing a Backup Drive


1. Reliability 2. Transfer speed 3. Time-to-data 4. Capacity 5. Compa8bility 6. Cost

Backup Media

Flash Memory Very expensive, small media, personal use only.

Super oppies ZIP 750MB, small capacity, high $/GB media.

Op8cal CD - cheap drives, small (650MB). DVD - cheap drives, but small (4.7GB) Blue-ray - more expensive, large (up to 12b GB)

Hard disk Large capacity, bulky, fragile, low $/GB media.

Tapes Large capacity (500GB), low $/GB media; expensive

drives.


Current Tape Formats

LTO (Linear Tape Open) Uses Ultrium format tapes. LTO3: 400GB capacity, 35 MB/s, 49s seek

Super DLT (Digital Linear Tape) Backward compa8ble with DLT formats. SDLT 600: 300GB capacity, 36 MB/s, 79s seek

SuperAIT (Advanced Intelligent Tape) SAIT-1: 500GB capacity, 30 MB/s, 45s seek


Common Tape Features

Form Factor 5.25 FH SCSI drives Fibre channel, SATA, USB, FireWire drives also exist Media are wide tape stored in cartridges.

Hardware compression Usually cited as 2:1, some cite higher. Depends heavily on nature of data stored.

Future Roadmaps Plans to double capacity in next few years. Tapes with capaci8es in the terabytes have been demoed (35 TB and 185 TB models)


Tape Autochangers

Stackers Works sequen8ally through a stack of tapes.

Autoloader / Jukebox Provides random access to set of tapes.

Library / Silo Mul8ple drives w/ random access to set of tapes. May incorporate bar code reader, ethernet, etc.


Backup SoBware

Linux defaults cpio, dump, rsync, tar

Open source AMANDA Bacula

Commercial Tivoli Storage Manager (IBM) Veritas Storage Manager


AutomaDon

The key to eciency and reliability. Use cron instead of manually backing up. Single tapes require manual media change. Tape libraries automate this process.

Other automated tasks Monitoring (up/down, disk space, security) Logs (rota8on, monitoring) File distribu8on


Cron

Performs tasks at scheduled 8mes. Crontab les specify schedule of tasks root: /etc/crontab users: /var/spool/cron/crontabs/*

Cron may log ac8vi8es and errors. Timing limita8ons: Runs tasks (if any) every minute. Does not perform scheduled tasks if system down. May or may not perform tasks on DST transi8on.


Crontab


Format minute hour day month weekday user command

Examples 30 4 * * 0 root yum y update 3 * * * * root (cd /var/www; make) 20 1 * * * root /usr/local/rot-logs

Managing Automated Tasks

Divide by 8me: Hourly, daily, weekly, monthly tasks

Crontab uses run-parts meta-script: 17 * * * * root run-parts --report /etc/cron.hourly 25 6 * * * root run-parts --report /etc/cron.daily 47 6 * * 7 root run-parts --report /etc/cron.weekly 52 6 1 * * root run-parts --report /etc/cron.monthly

Add crons by placing script in 8me directory. Add random delay if all hosts share same crontab.


Backup Security

Tape security Tapes contain all of your important data. Data isnt secure unless tapes are secure. Solu8ons: tape vault, encrypted tapes.

Backup server security Has read access to all important data. If backup server isnt secure, data isnt secure. Solu8ons: integrity checking, least privilege

Restore process Who can request les to be restored? Where will restored le be placed? What will its ACL be?


Chapter 10

Documents

computer science department

systems administra8on

backup schedule

backup sla

backup media

backup servers

backup types

backup security