Summary 49
Backups and Archiving
Backing up data is essential to the survival and continuation of integral operations. Anyone
in the support field who has spent an entire weeknight restoring a server can attest to this.
Let’s cover a few of the basic backup schemes you’ll see in the wild.
The archive bit is a file attribute that signifies to the system if and when a
file has been modified. This archive bit is then used in a backup scheme to
determine whether a file needs to be backed up.Full Backup A full backup resets the archive bit of all files and backs them up accordingly.
Differential Backup This backs up all changed files since the last successful full backup.
This job does not reset the archive bit. The reasoning behind not resetting the archive bit?
Each differential is always based on the last full backup. Thus, any changes made since that
last full backup are backed up...and backed up...and backed up. The benefit to this scheme
is that during a full restore, only the last full backup and the most recent differential are
needed to restore the entire site. The downside is that differentials can get huge!
Incremental Backup This job backs up all changed files since the last successful full
backup, or since the last incremental. An incremental backup does reset the archive bit.
What this equates to is a backup scheme that focuses on efficiency in the initial process.
How? Once an incremental scheme has performed an incremental backup based on the
last full, it bases all subsequent backups on the last incremental. In other words, you get a
bunch of small backup jobs, all with the most recent changes. What this translates into is
a tedious and lengthy full restoration job. The last full backup will need to be restored, as
well as all the incrementals up to the current date.
The intent here is not to make you a proficient backup operator, but to
make sure you understand the basics of each scheme and what kind of
impact the loss or compromise of such data can have on a company. Also,
from an exam perspective you should know the benefits of one restore
versus another (for example, the benefits of a full restore versus a differen-
tial restore).Summary
Two complementary yet opposing concepts are at play when talking about network topolo-
gies: logical topology (how traffic enters the network) and physical topology. Common
physical topologies are the bus, ring, star, mesh, and hybrid (the most common). A token
can be passed around for permission to transmit, or a shared media strategy can be used in
which nodes listen for an opening.