-: In the last lesson we mentioned cold sites and warm sites,
and for these to work you have to be able
to bring your data and get 'em over
to those new networks that you install there.
Well, to do that you have to have
a good backup to begin with.
Data backups can be conducted using full backups,
incremental backups, or differential backups.
Now, when I discuss each of these types
I'm going to use the word drive to describe
the way data is being backed up.
This can be the entire hard disk,
but it can also be just a file or a folder on that disk
depending on how you scope your backup configurations.
But for the purposes of my explanations
and these definitions, I'm just going to say drive
throughout the rest of the lesson to keep it easy.
Now, the first kind we have is known as a full backup.
When you do a full backup, all of the contents
of your drive are backed up, that's every single file.
Now, when we go to an incremental backup,
which is our second type, this is going to backup
only the contents of the drive
that have changed since the last full backup,
or since your last incremental backup.
Now, the third category we have is known
as a differential backup.
Differential backups will only backup the contents
of the drive that have changed since the last full backup.
So, let's say that every Sunday at 9:00 p.m.
I run a full weekly backup of the drive,
then the rest of the week I use a differential backup
to create backups of any files or folders
that have changed since Sunday when I did that full backup.
This is good because if I have a drive
fail on Wednesday, I can restore from the full backup
we made on Sunday and then the differential backup
that I made on Tuesday, and all the file changes
that happened on Monday and Tuesday
would also be included in that Tuesday differential backup.
Now, there is one problem with full backups,
they take a lot of time.
Differential backups take up less time,
but they can still take a while
if you have a lot of changes,
and so many organizations instead,
use what's known as an incremental backup.
Now, this only creates a backup of everything that's changed
since the last full backup,
or since the last incremental backup.
So let's go back to our example
and configure our backups for our server.
Let's say we decide to do a full backup
every Sunday just like before,
but instead of using a differential backup
we're going to use an incremental backup each night.
This is going to save us some time.
So, Monday we do an incremental,
Tuesday we do an incremental,
Wednesday I do an incremental,
Thursday I do an incremental, and Friday my drive fails.
Which backups do I need to use to restore all my data?
Well, instead of needing Sunday, the full backup,
and Thursday night, if we'd done a differential backup,
we're now going to have to go and get
every single one from Sunday, the full backup,
and then Monday's incremental,
Tuesday's incremental, Wednesday's incremental,
and finally, Thursday's incremental,
and we'll have to restore them in that order.
Now you can see the tough choice we have
between using incrementals and differentials,
because incrementals take a lot less time to backup,
but the differentials make it a lot quicker
when we need to restore,
and so this going to be a choice you have to make.
Do you want quick backups and lengthy restores,
or do you want long backups and quick restores?
(electronic beats)