Archiving and backing up

In this section we attept to explain the importance of backing up your data. We look briefly at the various technologies available and conclude with some hints and tips.

Backups

• Why?
  • The most valuable item on your PC is not the hardware or the programs, it is your data - do you really want to risk throwing away several years of (presumably) valuable work?
  • Hard disks do not last for ever - they are delicate electro-mechanical devices. If there's a problem with your disk, we will do everything possible to retrieve the data but there are times when nothing can be done.
  • It is not completely unknown for Microsoft Windows to crash and lose data.
  • To provide insurance against virus attacks.
  • To provide insurance against brain-fade - most users have discovered new and highly creative ways of losing files at some stage in their careers (if you haven't, you will).
  • If you are not the sole user of a PC, there's always a chance that one of your (much less-responsible) co-users may do something silly.

Choices of media

• Floppy Disk
  • Overview:
    • Once the default choice for most users but not necessarily the best. 3.5" disk drives can be found on most PCs although they are becoming less common.
  • Pros:
    • Floppy disk drives are available on most machines and thus easy to transfer to another machine. The disks are cheap (about 3 UKP / 10 disks) but their limited capacity makes them expensive and clumsy for larger backups.
  • Cons:
    • A limited capacity (1.44 MB) requires multiple disks for a backup of any size, i.e., not a realistic option for large backups.
    • Floppies are s-l-o-w, which tends to mean that some users (not you, of course) don't backup as often as they should.
    • Floppy disks are not a realistic option for arcival purposes as 3.5" disks are likely to go the way of 5.25" disks and large flightless birds.
    • Finally floppy disks are not noted for their reliability.
• Zip Disk
  • Overview:
    • A Zip disk looks like a floppy disk on steroids and works in much the same the manner.
  • Pros:
    • Zips have good capacity (100/250 MB).
    • They are much faster than floppy disks.
    • They are reasonably cheap; hardware about 50..100 UKP (depending on model) and disks about 7 UKP.
    • The disks are much more robust than floppy disks.
    • Zips can be treated as a small hard drive.
  • Cons:
    • Zips are not a standard feature on all PCs and can be expensive for large backups compared to CD-Rs
• Writable CD and DVDs
  • Overview:
    • The title says it all really; it looks like a CD-ROM but has the ability to write to CD-Rs and/or DVD-Rs. CD Burners about 30 UKP and DVD Burners 50 UKP
  • Pros:
    • This is the cheapest option for backing up a lot of data; good-quality disks are about 0.40 UKP with a capacity of 650 MB. DVD-Rs cost approximately 1 UKP but has a much greater capacity, 4.5 GB.
    • CD-Rs are readable on any PC with a CD-ROM; although there can sometimes be technical problems. DVD-Rs can be read on any PC that has a DVD-ROM.
    • Both are (probably) more robust than other formats and therefore particularly suited to long-term archiving.
  • Cons:
    • Writing to the disk can require a special program depending on the operating system and whether it is CD-R or DVD-R. This is typically provided with the hardware but is not entirely straightforward.
• USB Keys
  • Overview:
    • A keydrive is a small removable data storage device that uses flash memory and a USB connector.
  • Pros:
    • Keydrives are impervious to the scratches and dust that plagued previous forms of portable storage.
    • They are ideal for transporting personal data or work files from one location to another.
    • Most computers now have a USB connector on them which means that a drive will work in most places and that problems with device and driver incompatibilities are unlikely.
  • Cons:
    • If large storage is required it can become costly. 2GB can cost 100 UKP
    • Keydrives can sustain only a limited number of write/erase cycles before failure.
• External hard disk
  • Overview:
    • Like the title says the hard drives connect externally to the PC. Typically via USB 2.0 or Firewire.
  • Pros:
    • This is a good solution if you wish to mirror your hard drive or require large data storage.
  • Cons:
    • Cost makes them impractical for daily backups.
• File Server
  • Overview:
    • A shared network drive on a local file-server; from a user-perspective this is probably the best solution.
  • Pros:
    • The task of backup is centralised in the hands of your server administrator who should have a good backup strategy, i.e., an entire research group's data can be backed up together in a (hopefully) disciplined manner. This method can serve multiple users without any great problem.
  • Cons:
    • This method is relatively expensive since a dedicated server is required.

Backup tips

• Backup tips
  • Take a full backup regularly (say every month or so) and do daily differential backups during the intervening period.
  • Ensure that you have multiple backups - backups have been known to fail. The simplest approach is to alternate disk sets, e.g., have 2 sets of full and differential backups.
  • Keep backups either at geographically distinct locations (e.g., office and home - presupposing they're not the same) or keep a backup set in the School's fire safe.
  • Periodically test your backup by restoring some files
  • If you are backing up sensitive data either ensure that the backup is under lock and key or encrypted.
  • Use a backup program of some sort, e.g., Microsoft Backup which is a part of Windows. This will allow you to automate the backup and select between differential, incremental, and full backups.
  • For long-term backups (archiving) try to avoid, if possible, the use of proprietary file formats. For example, the chances of Word 97 doc files being loadable in 20 years time are about as good as loading a WordStar I file is today. This also extends to proprietary backup formats, such as Microsoft Backup; these programs have a nasty habit of being unable to read older backup formats.

Terminology

• Full backup
  • A backup which backups up all the files selected for backup. It is unusual to use this method on a daily basis unless you have either very little data to backup or a very fast backup medium.
• Differential backup
  • A backup which only backs up files that have changed since the last full backup.
• Incremental
  • Similar to a differential backup except files backed up in a previous incremental backup are excluded from future incremental backups.

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