Defragmentation |
| In the context of administering computer systems, defragmentation (or defragging) is a process that reduces the amount of fragmentation in file systems. It does this by physically reorganizing the contents of the disk in order to store the pieces of each file close together and in order (contiguously). It also attempts to create larger regions of free space using compaction to impede the return of fragmentation. Some defragmenters also try to keep smaller files within a single directory together, as they are often accessed in sequence. |
| Backup |
| Backup refers to the copying of data so that these additional copies may be restored after a data loss event. |
| Backups are useful primarily for two purposes: |
| 1. To restore a computer to an operational state following a disaster (called disaster recovery) |
| 2. To restore small numbers of files after they have been accidentally deleted or corrupted. |
| Backups differ from archives in the sense that archives are the primary copy of data and backups are a secondary copy of data. Backup systems differ from fault-tolerant systems in the sense that backup systems assume that a fault will cause a data loss event and fault-tolerant systems assume a fault will not. Backups are typical that last line of defense against data loss, and consequently the least granular and the least convenient to use. |
| Since a backup system contains at least one copy of all data worth saving, the data storage requirements are considerable. Organizing this storage space and managing the backup process is a complicated undertaking. |
| Backing up Files |
| Computer errors and software failures happen ocasionally so it is important to backup your files and documents. |
| One simple way to backup your files is to copy them to a disk. If there are only a few small files a floppy disk will work but if you are backing up lots of large files a cd burner, a second hard drive or tape backup may be needed. You can use a software program to automate backups or do it manually. A manual backup usually involves dragging the files or folders to the backup disk or tape to create the duplicate backup. |
| Store your backup files in a safe place out of the sun and away from electro-magnetic devices such as speakers and wires with strong electrical currents. |
| Every file that you create and plan to keep should be backed up. This includes word processing documents, financial information, databases, photos, etc… |
| Some less obvious files that also need to be backed up are email, Internet Favorites or Bookmarks, and Address Books. Check the help files in your email program on how to back up email. Generally, each folder name in your email program is a file containing the individual email messages and copying these files to the backup disk or tape will be sufficient. Software preferences such as customized menus and settings can also be backed up. Check your software’s help files to find out where these files are located. |
| A newer software version may be installed on the computer before ever needing the backups so make sure that the newer programs can handle the older file format. |
| When to backup is an individual choice. A company should have a backup policy which explains how and when data should be backed up. It all depends on how important the information is and how difficult it would be to duplicate it in the event of a system failure. If the information is critical an automatic backup system that duplicates the documents immediately may be needed (a Redundant Arrays of Inexpensive Disks (RAID) system is an example). If the files are not critical a weekly backup may be all that is needed. It is impossible to determine when a system failure will occur so it is better be cautious. |
| The backed up data can then be used as an archive, to recover from a system failure or to transfer data to a new computer system. Simply copy the files to the correct folder to restore them. Backup softwarewill have an automatic recovery feature that will restore the backed up file automatically. |
| Compression and Decompression |
| Most software you buy or get off the Internet is compressed. Computers store information in byteswhich are made up of on or off signals. The software applications that uses these files need to have all the on and off signals (bytes) in place but when the file is stored they can be modified to take up less space on the storage disk or tape. |
| There are commercial and shareware programs that will compress and decompressed files for you. The most popular form of data compression is called zip or stuffit but there are others available as well. |
| Programs are also available to compress and decompress your files as you or the application you are using requires them. This can be a way of making more space available on a hard drive. Windows comes with a program that will compress part of your hard disk. Be sure to read the documentation before embarking on a project like compressing a hard drive. |