Differential & Incremental

RS_MCP

IT Pro's,

Could someone please explain the difference between the two (excluding the tech notes info)

For some reason, I can not understand the terms.

Any scenario example would also help.

Thank you for reading this post.

Many Thanks.

Raj

Goldmember

I just took the test and hear is my knowledge.



Think of a differential backup as "difference" and incremental backup as "increment".
The difference backup should take the difference from the normal backup everytime it runs.
This means if I take 3 differential backup in a row they should all have the same data except the newest one will have the most recent changes.

The increment is used to take the change only from the last increment. If you have 3 increment backups in a row they will contain different data which will be sequentially ordered with increment1 being before increment2 and the last increment holding data from the change between increment 2.

The tricky part is MS throws in incremental and differential backups between each other which is why you must understand the archive attribute really well and its purpose.



The key to understanding the different backups is the archive atrribute.

This attribute is used by both backup methods when determining what data to backup. When a user makes a change or creates a new file the archive attribute will be checked.

What you need to understand is which method clears the attribute and which backup method does not clear the attribute. This will determine what gets backed up when both methods are used together. Otherwise if you only use one method and normal backup together, the backups are easy to understand.

Here is the breakdown

Incremental Backup = This method clears the archive attribute. It will backup data that only has the archive attribute checked, and when its done backing up it will uncheck(clear) the attribute.


Differential Backup = This method does not clear the archive attribute. It will backup data that only has the archive attribute checked, and when its done it will not uncheck(clear) the attribute.

What does this mean?


Both of these methods can be used in conjunction with a normal backup, which clears the archive attribute. Everytime you run incremental it will clear the attribute, and everytime you run differential backup it will not clear. Both backup routines rely on the archive attribute to be checked in determining what data to backup.


Any more questions?

Do some Measureup practice tests. They will help you understand.

RS_MCP

"Goldmember" Thank you for your post.

Much appreciated.

I will study this now...

I will be in touch.

Raj

Krank

It's simple, think about this:

Incremental - Increments the number of storage media. When restoring from back up you'll need the whole set of storage media plus the full back up that should have been done previously to the incrementals.

Differential - You'll need the latest incremental back up plus the full back up to restore information.

The process of backing up starts with a full back up. Then you decide between incremental or differential, depending on your needs.

- Incremental Back up backs up only the files that changed compared to the previous back up (full or incremental). These back ups are done quicker than differential but the restoring process is slower.
Example: You do a full back up on sunday, an incremental on tuesday and thursday and you want to restore the data on friday, so you'll need those 3 back ups.

- Differential Back up backs up all the files that changed compared to the previous full back up. These back ups are done slower than incremental but the restoring process is faster because you'll always need only 2 media.
Example: You do a full back up on sunday, a differential on tuesday and thursday and you want to restore the data on friday, so you'll need only 2 back ups, the latest differential (thursday one) and the full back up.

Incremental and Differential should never be combined.

I'm sorry if I'm not so clear but english is not my main language.