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AS - INFO2 - 6 - Backup and Recovery
Transcript of AS - INFO2 - 6 - Backup and Recovery
Individual Needs to backup and Recovery
The options for backup and recovery are dependent upon the following factors:
• Content & Type – What data needs to be backed up
• Frequency – How often should a backup take place
• Timing – When is the best time to backup
• Backup Media – What the data will be backed up onto
• Location – Where will the backup will be stored
• Responsibility – Who will make sure that the backup is carried out
• Testing & Recovery – Make sure that the backup has been successful.
Why BACKUP Data?
Look at the following examples:
In 1997, during a fire at the headquarters of Credit Lyonnais, a major bank in Paris, system administrators ran into the burning building to rescue backup tapes because they didn't have offsite copies.
Crucial bank archives and computer data were lost.
On 3 January 2008, an email server crashed at TeliaSonera, a major Nordic telecom company and internet service provider. It was subsequently discovered that the last serviceable backup set was from 15 December 2007.
Three hundred thousand customer email accounts were affected.
“Lost digital data cost businesses billions”
Backing up Data is making a Second copy of data. What would happen if the school did not backup your coursework and you deleted it?
Content & Backup Type
What type of backup? If it is large amounts of data is may not be a good idea to backup EVERYTHING EVERYDAY!
1. Full Backup
This is where all the data that needs to be stored is fully backed up each day. If a file needs to be restored you simply reload it from the last full backup taken.
However a full backup takes the most
time to store.
Full backups are the easiest concept to understand, but use the most storage space and take the most time to store.
However, they are the quickest method for restoring of data.
2. Incremental Backup
This method stores all files changed since the last FULL, DIFFERENTIAL or INCREMENTAL backup and it takes the least time to complete.
Incremental backups would normally be organised as follows in an organisation that operates 24/7.
The full backup is carried out on Sunday, when the least data processing is being carried out.
During an incremental backup only the files changed since the most recent backup are included.
That is where it gets its name: each backup is an additional increment since the most recent backup.
Incremental backup provides a faster method of backing up data than repeatedly running full backups.
During a restore operation, each incremental backup is processed, which could result in a lengthy restore job.
For example, if you did a full backup on Sunday and incremental backups on Monday, Tuesday and Wednesday, and the PC crashes on Thursday morning, you would need all four backup files (Sunday, Monday, Tuesday & Wednesday) to restore the work.
However, the advantages are that it is the fastest method for storing files with the lowest storage space requirements, but the disadvantage is that the restoration of data is the slowest.
3. Differential Backup
This method stores all files changed since the last FULL backup and it takes less time to restore data than from an incremental backup.
Use differential backup if you have a reasonable amount of time to perform backups.
Only two backup container files are needed to perform a complete restore, so if you need to restore data you will need only the last full backup and the last differential backup.
The main advantages are:
• Restore is faster than restoring from incremental backup
• Backing up is faster than a full backup
• The storage space requirements are lower than for full backup.
The main disadvantages:
• Restore is slower than restoring from full backup
• Backing up is slower than incremental backup
• The storage space requirements are higher than for incremental backup..
The backup policy will need to indicate where the data backups should be kept. It is always worth
considering the worst case scenario when choosing this option, such as:
• Local Copy of Data – It is essential to keep a backup copy of the data onsite to aid a swift recovery should a user accidentally delete or lose a file. This data would be locked in a fireproof safe for physical security purposes.
• Off Site Copy of Data – This should be stored on a regular basis and kept off-site in case of a natural disaster to the site, or fire or power failure. With the data intact the organisation can lease another data processing site and be up and running in a short time.
Larger organisations that rely solely on ICT systems for their day-to-day activities may well have their backup data at a spare site (or even several sites), which would allow them to be operating in a very short time.
Frequency & Timing
The backup system will need to be completed at regular intervals, but how frequently is very much dependent upon the frequency with which data changes.
Many organisations rely on carrying out a backup on a daily basis. The timing would then be chosen to have the least impact on the business.
Normally backups would take place at the end of the working day so that there was no impact on staff and production.
However in some cases it is necessary for data to be backed up as it changes; for example each new record or transaction entered into the system will be backed up immediately. So in cases where absolutely no data loss is acceptable the backup will be continuously in progress.
The system normally in place is to save each transaction into two different hard disks; this technique is called mirroring and
makes use of RAID drives (Redundant Array of Inexpensive Disks). The RAID arrays can be on one server or saved onto two servers in cases where downtime is not acceptable.
There are many advantages in continuous backups, particularly where organisations, such as banks and online shops are operating 24 hours a day as the system does not have to shut down to backup with the
consequent disruption to staff and the business.
Responsibility for Backup and recovery
It is essential that an organisation allocates responsibility for data backup and recovery.
This will involve organising, running and overseeing the backup procedures.
Since this is a very important role, the organisation needs to ensure that someone is always available to perform the task, for instance in the
case of absence; this can be aided by the introduction of a staff rota to include cover for absence.
The responsibility would include the carrying out of the backup at the correct intervals and storing the media at the agreed location, be it on-site and / or off-site.
Since there are most likely to be several backup disks in circulation, it will also be necessary to log which disk was backed up on which day.
Testing and recovery
Finally the responsibility would include the testing and recovery of the system, to ensure the backup is valid.
In most cases the backup is seldom used except in an emergency or when someone has erroneously deleted some files; therefore it is important that the backup is tested to ensure that data can be restored from it if necessary.
The Need for Continuity of Service
The Internet has moved hand-in-hand with global trading and as a consequence many online trading companies are now operating 24 hours a day for 7 days a week.
Since these operations are totally reliant on ICT systems there is an urgent need for companies to have continuous service from their critical computer systems.
Not all companies have sufficient resources and expertise to take all these precautions in which case they can buy into a continuous service provider to help them plan and insure against catastrophe; http://www.polygonenterprises.co.uk gives an indication of the help
and advice available.
The impact of power failure can be minimised by using a UPS (Uninterruptible Power Supply) so that if the power fails the server is closed down in a controlled manner.
Standby generators can also be used to take over in the event of mains failure from the utility company.
Server or ICT System Failure
The system can be supported by a team of trained technicians who have sufficient spares to fix the malfunction in a short space of time to minimise the disruption to service.
The system can be continuously backed up to a spare site,which could be a nearby building, so in the event of a major breakdown or natural disaster, the system can be operative in a short space of time.