One of the most important steps in maintaining a network is having backups. The question of if a hard drive will fail is not the correct question, but rather when it will fail. Data loss is a part of life. Preventing this loss requires backups. In this section we will discuss implementing backups. There are several forms of backup one can perform. The traditional form is known as a full-differential-incremental backup. This is being replaced by several different forms of backup, and we’ll discuss all these forms below.
1. Full-Differential-Incremental Backups.
The traditional form of backups is three step. The first is to take a first backup of all the files that need to be protected. Then on a daily basis one performs incremental backups. Incremental backups backup only the files that have since the last full, differential, or incremental backup. The final form of backup is differential. A differential backs up all files that have changed since the last full backup.
Generally one has two sets of backup medium. One performs a full backup when first inserting the medium and then follows this with incremenetals and differentials until the medium is full or a certain period of time has expired. Then one takes this media off-site and places in the second set of backup medium. One then repeats the steps. When that set is full go back to the first set.
2. Continuous Protection Backups.
Continuous Protection backups are revolutionizing the world of backups. The first time files are backed up they are backed up in their entirety. Then every additional time only the portions of the files that have changed are backed up. It is somewhat similar to incremental backups, but in traditional incremental backups one had to apply the full backup, then each incremental up until the date you wanted. Whereas Continuous Protection creates a patchwork that makes it possible to choose a file or multiple files from a certain date and restore them without having to go through the tedious process of applying multiple backups.
Besides these two basic forms of backups there are several variations within these backups:
1. Plain File Backups – The traditional method of backups is to backup the individual files, just as if they were on the hard disk.
Pros: Makes it easy to pull individual files off.
Cons: Is difficult to restore an entire system in the case of a disaster (e.g. complete computer failure).
2. Image Based Backups – Backs up an entire drive, especially useful in cases where one needs to restore an entire server or workstation environment.
Pros: Makes it easy to restore an entire system in the case of a disaster (e.g. complete computer failure).
Cons: It isn’t quite as easy to restore individual files.
3. Removable Media Backups – Uses removable media to backup information, traditionally tapes but recently this has moved to included removable hard disks and optical disks (e.g. DVD’s).
Pros: In the case where a location is destroyed (fire, natural disaster, terrorism) the information is available at a remote location.
Cons: Tapes are a linear medium that takes a long time to restore from. Hard Disks and Optical Disks are better, but Optical especially as lifespan issues.
4. Disk to Disk Backups – Takes information from one hard drive and copies it to another thus placing the content in two locations.
Pros: The files are available for restore in minutes. There is no need to go off-site to retrieve the medium or to use linear media. It also allows for continuous backup.
Cons: In the case of a disaster you are in trouble. Both your primary and backup data was located in the same building.
5. Disk to Disk to Removable Media Backups – Copies the content to two disk locations and then onto removable media which can be taken off-site.
Pros: Offers the convenience of Disk to Disk without the dangers therei.
Cons: One still has to manage tapes or disks.
Pros: Gives the advantages of disk to disk without the dangers and while cutting out the removable disk.
Cons: Can be expensive if you have large amounts of data and can take a while to restore across a WAN if the amount of data is large.
Let’s conclude by discussing a few software options that can help make a successful backup plan a reality. For most businesses I recommend Mozy Pro. Mozy charges a flat fee per license per month ($3.95/mo.) and then a per-gigabyte monthly charge as well ($0.50/mo.). For most businesses this is a very affordable option as they are mainly storing text, spreadsheet, and presentation documents which are relatively small, and for less than $10/mo. they can backup an employee’s critical information. Mozy is great because it offers off-site backup, the data is highly encrypted, and it uses bit-differential technology – which means that after the initial backup only the data that changes is transferred.
On the other hand, if you are a consumer of larger amounts of data you will probably need to go with a different solution – one hosted by yourself. The price per gigabyte becomes prohibitively expensive when you need more than a few dozen gigabytes. In these cases one good choice is utilizing two software programs that Symantec offers (through its acquisition of Veritas): Backup Exec for Continuous Protection and Backup Exec 11d. CPS can be used to continuously backup information to disk, from whence you can use 11d to backup data to removable storage. If you have Exchange you should purchase the CPS agent for Exchange and you should also purchase the Desktop Laptop Option to continuously protect your desktops and laptops (CPS is only for servers).