What is a data backup and how do I restore data backups?

• What is a Data Backup?
• How Do I Restore Data Backups?

What is a Data Backup?

A data backup consists of copying or archiving files for the purpose of being able to restore them in case of data loss.

Data loss can occur from many sources ranging from computer viruses to hardware failures to file corruption to fire, flood, or theft and so on. If you're a business, you may have lost critical financial, customer, and company data. If the data resides on a personal computer, you could lose financial data and other key files, pictures, music, etc that would be hard to replace.

As part of a data backup plan, you should consider the following:

1. Which files to backup
2. How often to backup
3. What kind of backups to run
4. What kind of media on which to store the backups
5. Where to store the backup data for safekeeping

Some examples of different possible data backup strategies and also some different restore scenarios are listed below.

Which files to back up

In general, you should back up any work or data that can't be replaced easily. Some examples are word processing documents, databases for financial data, customer data, and personal files such as pictures, music files, emails, etc.

As a rule of thumb, do not backup programs. Programs themselves will need to be reinstalled. Be sure to have program installation discs and registration information archived.

How often to backup

The frequency to run the backups depends on how often the data changes. Businesses where data changes frequently may run daily or hourly backups. If your data only changes every few days, you might not need to run backups as often. The WinZip® Job Wizard in WinZip Pro allows you to schedule your backups to run at a specified time automatically so that you don't have to remember to run it manually.

What kind of backups to run

You can run the following kinds of backups: Full Data Backup, Incremental, or Differential. In WinZip's Job Wizard, in addition to Full Data, Incremental, and Differential backups, you also have the option to run a Normal backup and an Update backup. For a more complete description of the different job types, please view the topic Choose Job Types in the WinZip Job Wizard help.

Things to keep in mind:

• You should create new backup archives or rotate through multiple archives whenever you run the backup instead of continually overwriting or updating only one file. The reason is that in case the backup process goes wrong or the file becomes corrupt, you have not overwritten or corrupted a good copy of the archives. See the examples below for possible backup strategies.
• A Full Data Backup will require the most storage space of the different types.
• An Incremental Backup will only back up the files that have changed since the last Full Backup or Incremental Backup; therefore the storage requirements for these archives are usually the smallest.
• A Differential Backup will back up all of the files that have changed since the last Full or Incremental Backup; however, because it does not reset the archive attribute of the files, storage requirements for differential backup archives may be greater than for incremental backup archives. For example, if a Full Backup is run on Sunday, and then a Differential Archive is run on Monday, the Monday differential archive will contain any files that have changed from Sunday (after the full backup) to Monday. If another Differential Backup is run on Tuesday, then Tuesday's differential archive will include all of the files that have changed between Sunday and Tuesday. You can see that the differential archive files may grow quite large depending on how often that a full or incremental backup is run and how many files change during that time period.

What kind of media to use to store the backup and where to store the backups

We won't fully address these last two questions since they are beyond the scope of WinZip. However, you can store the archives on a tape, a CD/DVD, another hard drive, etc. One thing to keep in mind is that you should not store the backup on the same hard drive as the files that you're backing up since if anything happens to that hard drive, then you've lost both the originals and the backups. WinZip's Job Wizard makes it easy to create an archive on another hard drive or network location or a CD/DVD (assuming that the whole archive will fit on one CD/DVD.)

As far as where to store the archives, optimally, you should keep a copy of the backup files on-site for easy access and a copy off-site in case of fire, flood, or other damage to your location which could damage or destroy the on-site backup copy.

Some possible backup strategies

In the strategies below, we'll use the term "archive" to denote the archived data stored on a media, whether that media is a hard drive, cd/dvd, tape backup, or some other medium.

Strategy 1: perform a Full Data Backup every day in two or more archives.

This strategy will only be viable for situations where you're only backing up a few files. You will want to use at least two archives to reduce the risk of being totally without recourse if one of the backups becomes corrupt or damaged.

Strategy 2: using 3 archives using Incremental Backups.

• Archive 1: a Full Data Backup on even weeks performed every other Friday.
• Archive 2: a Full Data Backup on odd weeks performed every other Friday.
• Archive 3: an Incremental Backup that is updated daily for all other days: Monday, Tuesday, Wednesday, and Thursday.

With this strategy, if your incremental backup in archive 3 is damaged then you've only lost the data since the last Friday backup. You would also keep the older of the Full Data Backups off-site in case of disaster at the site.

Strategy 3: using 6 archives using Incremental Backups.

• Archive 1: a Full Data Backup on even weeks performed every other Friday.
• Archive 2: a Full Data Backup on odd weeks performed every other Friday.
• Archive 3: an Incremental Backup on Monday.
• Archive 4: an Incremental Backup on Tuesday.
• Archive 5: an Incremental Backup on Wednesday.
• Archive 6: an Incremental Backup on Thursday.

Using this strategy, if any incremental backup is corrupt, then you still have all the changes from the other incremental archives and you only lose the data from the corrupt Incremental Backup. You would also keep the older of the Full Data Backups off-site in case of disaster at the site.

Strategy 4: using 6 archives using Differential Backups.

• Archive 1: a Full Data Backup on even weeks performed every other Friday.
• Archive 2: a Full Data Backup on odd weeks performed every other Friday.
• Archive 3: a Differential Backup on Monday.
• Archive 4: a Differential Backup on Tuesday.
• Archive 5: a Differential Backup on Wednesday.
• Archive 6: a Differential Backup on Thursday.

Using this strategy, if archives 3, 4, or 5 become corrupt and archive 6 is still good, you haven't lost any data. If archive 6 becomes corrupt, then, assuming archive 5 is still good, you will only lose the data from Thursday. You would also keep the older of the Full Data Backups off-site in case of disaster at the site.

How Do I Restore Data Backups?

You have one or more Zip files that contain data you want to restore to your computer. How do you do that?

The simplest answer is to open the Zip file and click on the Extract toolbar button or click Extract from the Actions menu. This will open the Extract dialog which will allow you to specify certain options and extract the contents of the Zip file into a location that you specify.

However, if you have multiple Zip files created using different job types in the WinZip Job Wizard, then the restore process may be a little more complex. For descriptions of the different Job Types, please see the WinZip Job Wizard help.

Here are some scenarios to illustrate the data restore process:

Scenario 1:

• Create a Normal backup on Monday.
• Create a Normal backup on Tuesday.
• Create a Normal Backup on Wednesday.
• Hard drive crashes on Thursday.

To restore this, do the following:

• Restore the data from the Zip file created on Wednesday; it should contain the latest set of data already.

Scenario 2:

• Create a Full Data Backup on Monday.
• Create an Incremental Data Backup on Tuesday.
• Create an Incremental Data Backup on Wednesday.
• Hard drive crashes on Thursday.

To restore this, restore the backups in the following order to ensure that you have the latest versions of all data files:

• Restore Monday's Full Data Backup.
• Restore Tuesday's Incremental Backup.
• Restore Wednesday's Incremental Backup.

Scenario 3:

• Create a Full Data Backup on Monday.
• Create a Differential Data Backup on Tuesday.
• Create a Differential Data Backup on Wednesday.
• Hard drive crashes on Thursday.

To restore this, restore the backups in the following order to ensure that you have the latest versions of all data files:

• Restore Monday's Full Data Backup.
• Restore Wednesday's Differential Data Backup; it already contains all of the files that have changed since Monday.

As you can see, you may save time with the restore process when using Differential Data Backups in your backup plan. However, it can also use up more space for the backups since you may be saving more files in the differential archives than with the incremental archives. It can also take longer to create the differential archives since they may be archiving more files, depending on how many files have changed since the last full backup and how long before the next full backup; whereas, since the incremental archives only have the files that have changed since the most recent incremental or full data backup, the archives may be smaller and take less time to create.