Data Backup and Recovery Heng Sovannarith heng_sovannarith@yahoo.com
Introduc=on Because data is the heart of the enterprise, it's crucial for you to protect it. And to protect your organiza=on's data, you need to implement a data backup and recovery plan. Backing up files can protect against accidental loss of user data, database corrup=on, hardware failures, and even natural disasters. It's your job as an administrator to make sure that backups are performed and that backup tapes are stored in a secure loca=on.
Crea=ng a Backup and Recovery Plan With a solid backup and recovery plan, you can recover from any of these. To help you create a plan, consider the following: How important is the data on your systems? What type of informa5on does the data contain? How o7en does the data change? How quickly do you need to recover the data? Do you have the equipment to perform backups? Who will be responsible for the backup and recovery plan? What is the best 5me to schedule backups? Do you need to store backups off- site?
The Basic Types of Backup There are many techniques for backing up files. The techniques you use will depend on the type of data you're backing up, how convenient you want the recovery process to be, and more. The basic types of backups you can perform include Normal/full backups All files that have been selected are backed up, regardless of the senng of the archive aoribute. When a file is backed up, the archive aoribute is cleared. If the file is later modified, this aoribute is set, which indicates that the file needs to be backed up. Copy backups All files that have been selected are backed up, regardless of the senng of the archive aoribute. Unlike a normal backup, the archive aoribute on files isn't modified. This allows you to perform other types of backups on the files at a later date.
The Basic Types of Backup (cont.) Copy/Mirror backup is iden=cal to a full backup, with the excep=on that the files are not compressed in zip files and they can not be protected with a password. A mirror backup is most frequently used to create an exact copy of the source data. It has the benefit that the backup files can also be readily accessed using tools like Windows Explorer. Differen5al backups Designed to create backup copies of files that have changed since the last normal backup. The presence of the archive aoribute indicates that the file has been modified and only files with this aoribute are backed up. However, the archive aoribute on files isn't modified. This allows you to perform other types of backups on the files at a later date. Incremental backups Designed to create backups of files that have changed since the most recent normal or incremental backup. The presence of the archive aoribute indicates that the file has been modified and only files with this aoribute are backed up. When a file is backed up, the archive aoribute is cleared. If the file is later modified, this aoribute is set, which indicates that the file needs to be backed up.
Normal/Full Backup
Differen=al Backup
Incremental Backup
Copy/Mirror Backup
Comparison of backup type
Differen=al and Incremental Backups The difference between differen=al and incremental backups is extremely important. With differen=al backups you back up all the files that have changed since the last full backup (which means that the size of the differen=al backup grows over =me). With incremental backups, you only back up files that have changed since the most recent full or incremental backup (which means the size of the incremental backup is usually much smaller than a full backup).
Differen=al and Incremental Backups (cont.) Day of Week Weekly Full Backup with Daily Differen5al Backup Weekly Full Backup with Daily Incremental Backup Sunday A full backup is performed. A full backup is performed. Monday Tuesday Wednesday Thursday Friday Saturday A differen=al backup contains all changes since Sunday. A differen=al backup contains all changes since Sunday. A differen=al backup contains all changes since Sunday. A differen=al backup contains all changes since Sunday. A differen=al backup contains all changes since Sunday. A differen=al backup contains all changes since Sunday. An incremental backup contains changes since Sunday. An incremental backup contains changes since Monday. An incremental backup contains changes since Tuesday. An incremental backup contains changes since Wednesday. An incremental backup contains changes since Thursday. An incremental backup contains changes since Friday.
Selec=ng Backup Devices and Media Many tools are available for backing up data. Some are fast and expensive. Others are slow but very reliable. The backup solu=on that's right for your organiza=on depends on many factors, including Capacity The amount of data that you need to back up on a rou=ne basis. Can the backup hardware support the required load given your =me and resource constraints? Reliability The reliability of the backup hardware and media. Can you afford to sacrifice reliability to meet budget or =me needs? Extensibility The extensibility of the backup solu=on. Will this solu=on meet your needs as the organiza=on grows? Speed The speed with which data can be backed up and recovered. Can you afford to sacrifice speed to reduce costs? Cost The cost of the backup solu=on. Does it fit into your budget?
Common Backup Solu=ons Capacity, reliability, extensibility, speed, and cost are the issues driving your backup plan. If you understand how these issues affect your organiza=on, you'll be on track to select an appropriate backup solu=on. Some of the most commonly used backup solu=ons include Tape Drive: Tape drives are the most common backup devices. Tape drives use magne=c tape cartridges to store data. Magne=c tapes are rela=vely inexpensive but aren't highly reliable. Tapes can break or stretch. They can also lose informa=on over =me. The average capacity of tape cartridges ranges from 100 MB to 2 GB. Compared with other backup solu=ons, tape drives are fairly slow. S=ll, the selling point is the low cost.
Common Backup Solu=ons (cont.) Removable disks: Removable disks are increasingly being used as backup devices. Removable disks offer good speed and ease of use for a single drive or single system backup. However, the disk drives and the removable disks tend to be expensive. Disk drives: Disk drives provide the fastest way to back up and restore files. With disk drives, you can o`en accomplish in minutes what takes a tape drive hours. So when business needs mandate a speedy recovery, nothing beats a disk drive. The drawbacks to disk drives, however, are rela=vely high costs and less extensibility.
Common Backup Solu=ons (cont.) Magne5c op5cal drives: Magne=c op=cal drives combine magne=c tape technology with op=cal lasers to create a more reliable backup solu=on. Magne=c op=cal drives use 3.5- inch and 5.25- inch disks that look similar to floppies but are much thicker. Typically, magne=c op=cal disks have capaci=es of between 1 GB and 4 GB.
Common Backup Solu=ons (cont.)
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