Here is a first cut at a backup tutorial. Comments to correct errors or omissions are welcome. If there is enough interest perhaps it could be added to the wiki.
1.0 Why backup?There are four good reasons to backup data.
1.1 Data Loss Prevention1.1.1 Hard Drive Failure
All hard drives will eventually fail; it's just a question of when. Good failure rate data is hard to come by, and the rate of failure is influenced by many factors including temperature, vibration, power quality, design, and manufacturing variability. The best report I have seen was a study conducted by Google on their server farms. It indicated that the failure rate is much higher than you might expect - something like 20% of all drives within 5 years. My personal experience has been that 1 of my 15 drives fail about every 2 years. I expect this to increase as they age.
Sometimes drives fail with advance warning like a noise or operating system message. Other times they die with no warning. If you do lose a drive, and it's not making a clickity-clack sound, there is a reasonable chance you can recover the data with a good tool like SpinRite, but don't count on it.
1.1.2 Data Corruption (power failure, application bug, system crash, virus, etc.)
Even with a healthy drive you can still lose data for a variety reasons including power failure, motherboard failure, application bug, system crash, or malicious virus. My personal experience has been that these types of data loss are very rare.
1.1.3 User Error
Every user makes a mistake from time to time. Sometimes these user errors result in data loss or bad data. Sometimes you may not realize you made a mistake until days or weeks or months later.
1.1.4 Theft
A newish computer will be a priority target if your home is broken into. A laptop left in a vehicle lasts about 30 minutes in my town.
1.1.5 Disaster (fire/flood/earthquake)
Judge the risk for your own location.
1.2 Previous Version RestorationYou may encounter the need to restore a previous version of a file (see above 1.1.3).
1.3 Data PortabilityIf you backup your data on a portable device (like an external USB drive) then in addition to having a backup you also have a means of taking your data with you. In my case, I like having my data with me when I travel and my laptop drive is not big enough so I rely on external drives.
1.4 Drive Health Checkup & Preventative MaintenanceYou won't know if your drive has a problem unless you attempt to read it. Therefore, regular backups, in addition to backing up your data, also act as drive health checkups by letting you know that the drive is still ok.
Modern drives have a lot of intelligence and rely heavily on error correction to achieve today's amazing densities. Drives monitor the error correction rate for each disc sector they read, and when the error rate climbs sufficiently high they automatically flag the sector as bad and copy the data to a replacement sector. For this reason it is a good preventative maintenance practice to force your drive to read every sector from time to time. Making a complete backup is a good way to achieve this while accomplishing something else useful at the same time.
2.0 What backup device/media to use?2.1 Hard DriveGiven their low cost per GB and excellent performance nothing beats a hard drive as a backup device for large amounts of data. There are several ways to use hard drives for backup, but in all cases you should backup to a different physical drive. Never rely on a backup to the same physical drive (see above 1.1.1, 1.1.2, 1.1.4, and 1.1.5). Also be aware that one physical drive can be partitioned into multiple logical drives that you see in Windows; so make sure you know what drives are in your system and how they are configured. The Windows tool Administrative Tools\Computer Management\Storage\Disk Management provides a nice view of your drive setup.
2.1.1 RAID
RAID uses multiple physical drives to achieve data redundancy in one logical drive, and can protect you in a transparent way from a drive failure. There are pros and cons for using RAID. On the plus side, you are protected from a drive failure without having to do anything. On the minus side, RAID adds complexity which adds failure mechanisms, and it scrambles your data across multiple drives which can be inconvenient at times. I personally don't use it. Others swear by it. I am not going to discuss RAID further in this tutorial.
2.1.2 Extra drive in same system
On the plus side you get maximum drive performance. On the minus side you are not protected from theft or disaster, and your data is not portable.
2.1.3 Drive in different system on network
On the plus side you get more tolerance to theft. On the minus side, a wired network is about 2x slower than a local drive (and a wireless network is about 10x slower). I do not recommend using a wireless network if you copy more than a few gigabytes on a regular basis.
2.1.4 External USB/eSata drive
Mostly pluses here. USB drives are faster than network drives, and eSata drives are as fast as internal drives. In addition, if you disconnect and hide the external drive when not in use you achieve good tolerance to theft. And your data is portable. The only negative is clutter from yet another device with its own power brick and cable.
There is another possible advantage to using external drives for backup that is not often discussed. Some people believe that hard drive life is extended by leaving them powered up. Other people believe that drive life is extended by powering them down when not in use. Other people believe that frequent power up/down cycles reduce drive life. I do not know what the truth is. I therefore keep my desktop system on and my external drives off on the assumption that if someone is right then I have all the bases covered. In addition, if my home gets hit by lightning my powered down external drives should survive.
2.2 DVD-RThis is a cheap and simple (but slow) solution for modest amounts of data. The primary advantage of backing up to dvd-r is that you create a read-only snapshot of data, and assuming you keep old backups, it means you have a simple way to recover earlier versions of files. I backup my personal data (like databases, finances, email, etc.) once a month to dvd-r (because it is slow), and once a day to a different hard drive (because it is fast).
2.3 USB Flash Memory DrivePrices are dropping and capacities are increasing. Read speed is excellent. Write speed is slow (about the same as a wireless network drive). The primary advantage is convenient portability. I keep all of my personal data on an 8GB drive in my wallet. But I only update it about once a week because of its slow write speed.
3.0 What data to backup?Imagine losing your data. Then think about your level of pain. In my case, I back up everything.
A quick comment on data encryption. You should think about data security when designing your backup system and make a conscious decision whether to encrypt your data. In my case, I decided to only encrypt the data on my USB flash drive because I keep it in my wallet and the probability of loss or theft is reasonably high. Check out the excellent free TrueCrypt tool if you are interested in encrypting your data.
4.0 How many backups?At least one. Preferably two. I maintain two hard drive backups of all important data like my photos and media. My assumption is that the probability of two drives failing at the same time is very low but not impossible, especially if you consider theft or lightning strikes; whereas the probability of three drives failing at the same time, assuming one is a powered off and hidden external drive, is vanishingly small.
5.0 How often to backup?It depends on the value of your new files, how often you change files, and the effort you expended to change them. I backup all data that I change on the same day that I made the changes. On the other hand, I only backup my system (Windows and programs) about once a month because reconstructing a month's worth of system changes would not be that painful.
Continued here...
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