Fault Tolerance and Disaster Recovery

Topics Using Antivirus software Fault tolerance –Power –Redundancy –Storage –Services Disaster Recovery –Backup/Restore –Offsite storage –Hot and Cold spares –Hot, warm, and cold sites

Assessing Fault Tolerance and Disaster Recovery Needs A proper disaster recovery plan encompasses planning and preparing for a network disaster, but also recovering from it. A disaster is anything that destroys data or attempts, either deliberately or accidentally, to impair network operation. Disaster recovery is often taken too lightly and many administrators come to regret it.

Prepared for Disaster Hot site Warm site Cold site

Hot Site In a hot site, every computer system and piece of information has a redundant copy. This level of fault tolerance is used when systems must be up 100 percent of the time. Hot sites are strictly fault-tolerant implementations, not disaster recovery.

Two Levels of Clustering Failover Clustering –Active and passive servers –Uses a heart beat to detect failure Advantages and Disadvantages True Clustering –Supports multiple devices –Provides load balancing Advantages and Disadvantages

Fault Tolerance One system fails, one takes over 100% of clients

Warm Site In a warm site, the network service and data are available most of the time. The data and services are less critical than those in a hot site. The most commonly used warm-site technology is a duplicate server. This is Disaster Recovery not fault- tolerance

Cold Site A cold site cannot guarantee server uptime. If a server fails, the IT personnel will do their best to recover and fix the problem

Power Management Surge Protectors Battery Backup Line Conditioners Power management is for fault tolerance

Surge Protectors Level of Protection –Only covers Over-voltage –Common Components Active Protection Light Site Wiring Fault Light Ground IEEE 587 Category A (ANSI/IEEE C62.41) Let-Through UL Listing Circuit Breaker Additional Ports

Battery Backup Battery backup systems protect computer systems from power failures. –Under-Voltage Brown outs Black outs –Two Main Types of Battery Backup Standby Power Supply Uninterruptible Power Supply

Standby Power Supply Power is supplied from the AC unit Battery is backup only Uses a micro-switch to change power sources in the event of a power failure –They may include: Surge protection Multiple outlets Line voltage indicator Batter power indicator System management port

Uninterruptible Power Supply Power is supplied through the battery Batteries must be replaced regularly –They may include: Multiple outlets Line voltage indicator Batter power indicator System management port

Line Conditioners Dirty power introduces noise in the system. This can cause many types of problems, including –random lockups, –random reboots, and –system crashes.

Disk System Fault Tolerance Mirroring Duplexing Data striping Redundant Array of Independent (or Inexpensive) Disks (RAID)

Partitions Primary partitions Extended partition with logical drives Physical disk CC DD E F G

RAID Data written to multiple disks Data can be restored if one disk fails

Striping (RAID 0) Data DDAATTAA

Mirroring or Duplexing (RAID 1) Disk controllers Data DATADATADATADATADATADATADATADATA Drive 0Drive 1Drive 0Drive 1 Mirroring Duplexing

Striping with Parity (RAID 5) Data DD DD DD DD ParityParity ParityParity AA DD AA AA ParityParity TT AA AA TTParityParity AA TT TT TT ParityParity AA AA AA AA

Backup Considerations Backup Media Options Small-Capacity Removable Disks Large-Capacity Removable Disks Removable Optical Disks Magnetic Tape

Backup Policies Backup policy Testing Hardware and media Administration Software

The Standard Procedure for Database Backup Procedure for backing up a database: 1.Take database offline 2.Back up the database files 3.Clear the circular logs 4.Put the database back online

Standard Procedure for Database Restoration Procedure for restoring a database: 1.Take database offline 2.Restore database from latest tape 3.Put database back online and do not allow clients to connect 4.Play back the circular logs 5.Allow users to connect

Data Backups Your company’s last line of defense Considerations: What value does the data have? How will the backup be stored? Tape Disk Cloud What procedure will be used?

Backup Media Types Tapes Hard disks CD- and DVD-ROMs Cloud services

Backup Types Full Differential Incremental Full backup Amount of data 100% 50% Amount of data % 50% 100% 50% Full

Backup Types TypeWhat is Backed up Archive Bit Cleared? Number of sets to restore FullAll DataYesFull only DifferentialSince Last Full Backup NoFull plus Last differential IncrementalSince Last Backup YesFull plus every daily incremental to the last Full backup

Monthly tapes: 12 plus 1 extra Daily tapes: 4 for Mon – Thur, plus 1 extra Weekly tapes: 4 Fridays, plus 1 extra The GFS Rotation Method

The Tower of Hanoi Rotation Method Day Media Set Used Every A2 days B4 days C8 days D & E 16 days alternating between set D and E AAAAAAAA BBBB CC D E

Maintaining a Data Backup System Backup maintenance Maintain the data integrity Test your backups Maintain your hardware Inspect tapes Clean drives

Data Backup System Maintenance Verify backups Test restoration Review logs Replace tapes on schedule Maintain tapes and tape drives Clean tape drives Replace damaged tapes

Backing Up Remote Users and Workstations 1.Must be online and powered up 2.Remote users may require a method of backup that allows them to back up from the road 3.Consider Web-based backups

Specialized Data Backups Enterprise backupsMobile users Power user workstations Open filesDatabase

Virus Protection Types of Viruses –File Viruses –Macro Viruses –Boot Sector Viruses –Hoax Virus

Updating Antivirus Components A typical antivirus program consists of two components: –The definition files –The engine

Scanning for Viruses Two types of antivirus scans: –On-demand –On-access

Software Revisions Is It Necessary? Where to Get Patches How to Apply Patches

Summary Exam Essentials Review Questions