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<h2 class="style1">(Some) Backup theory</h2>
<p class="style2">In this document I will discuss about the theory
of backups. I will analyze such questions as: What is a backup? Do
I need to backup all my systems files or only my data? Do I need
compression? Do I need to use Volume Shadow Copies? & and other
important questions.
<p class="style2">Everything expressed here is my opinion only and
should not be taken as the one and only truth . This is the way I
make my backups, and how my mind works when I m planning them.
<h4>What is a backup and why do I need to backup my files? </h4>
<p class="style2">In the computer world, a backup is a copy of some
data. This copy could be used to restore the original data when the
original information is lost or damaged. You can make backups of
your data manually, by copying your files to another place: a CD,
another disc, another machine, to a tape device, etc, or it can be
made automatically, by scheduling a backup.
<p class="style2">Ideally, the copy should be stored on another
physical place and should not be stored on the same room where the
original is. In case of disaster, like a fire, having both the
original data and the backup on the same physical place could be
fatal. I recommend you to make multiple copies of your valuable
data: for example, you can have a copy stored on another hard drive
and another copy on some remote FTP server, for maximum security.
<h4>Do I need to make a backup? Why do I need Cobian Backup? </h4>
<p class="style2">Yes, you need to make backups of your files,
unless you don t care about your data at all. Do you need
Cobian Backup? Actually not at all. You can make your backups
manually, but it s very easy to forget to backup your files
regularly. Your data is often not static, it may change often and
you need to be careful and backup any changes you do with your data.
Cobian Backup just helps you to setup your backup and forget about
it . It will then back up your files for you without any human
interaction.
<h4>Permissions are the Alpha and the Omega of a modern OS</h4>
<p class="style2">In a modern multiuser operative system, everything
is controlled by access rules (or permissions, for simplicity).
Every process that is executed on the computer has an owner, and it
can only have access to those resources that the owner is allowed to
use.
<p class="style2"> But, I am the only user on my computer. I know
that say many people. Wrong, think again. Every default Windows
installation includes many other users that are not you (even if you
don t even think that they exist). For example: the local System
account is the default account used to execute Windows Services.
Guest, Administrator, ASPNET, HelpAssistant, etc are other accounts
that may exist on your computer.
<p class="style2">If you are executing the backup program as the
user A and want to back up the disc C:\, which includes files which
are owned by the user B, it s very probable that this operation will
fail, because A by default shouldn t have access to B s files.
<p class="style2"> But I m running the program as an Administrator.
I have access to all files - This is another myth. And sure it seems
logical that the almighty Administrator should have access to all
files, but& that is not necessarily true. Being an Administrator
means that you can potentially access any file but if some user (or
the system) eliminates the Administrator as a member of the list of
allowed users, guess what& the backup program will not have access
either to those files.
<p class="style2">In Vista, it's also especially important to know
that even when running as an administrator, your program could be
executed with limited powers if you have UAC activated.
<p class="style2">Then we have some other kind of permissions:
policies, which can also limit an account in several ways. For
example, the local System account cannot access network resources by
default.
<p class="style2">In my experience, in the 9 years offered support
for Cobian Backup, I can tell that more than 70% of the problems
that the users experiment are just problems with permissions and
could be easily solved if the user only could educate him- or
herself a little about how permissions work on a Windows system.
<h4>Do I need to backup system files or only my data? </h4>
<p class="style2">Well, it depends. Some people prefer to back up
the whole system (OS plus data files). Yes, today storage is really
cheap and all, but & backing up the thousand of files in different
states that a modern OS has is not a trivial task, it takes a lot of
space, a lot of time, and storing it on a remote machine can be a
nightmare for your internet connection. For me: I backup what is
REALLY important and irreplaceable: my data files.
<p class="style2">The system can be re-installed from the original
media. Your programs can be re-installed as well, but& your data?
Your documents, spreadsheets, databases, photos& . That cannot be
re-created as easy. And THAT is what you need to care about.
<h4>Do I need compression? And Encryption? </h4>
<p class="style2">Compression is a good thing in theory. You have X
bytes of data and, voila, now you have the same data, but using less
space. There are different methods of compression and all of them
have different advantages/disadvantages in relationship to the
other. But compression as cool at it seems has actually some
disadvantages: all your data is stored in one file, so if only one
byte on that file is corrupted, you can lose all your data at once!
<p class="style2">Compression is often a slow process, much slower
than a plain copy. Updating a large archive takes also a lot of time
and sometimes you need a lot of extra-space as well. Compressing
directly to a remote location can eat a lot of bandwidth as well.
Many files like mp3, jpg, etc compress very badly because they are
already compressed, you may be wasting your time compressing them.
Oh, and did I say that storage is very cheap these days? That may
sound like I m against compression. Well, I m not, really. But I
don t use it for my backups.
<p class="style2">Encryption? That depends on your data. You may
not need encryption at all. You maybe already have an encrypted
volume (NTFS drives can use encryption), or maybe you are using a
TrueCrypt volume as your destination. In those cases you don t need
an extra layer of encryption, unless you are *very* paranoid about
your data.
<p class="style2">Sometimes it may be enough to use NTFS file
permissions to prevent the access to your backup files. Bear in mind
that encryption is also a slow operation.
<h4>Do I need to use Volume Shadow Copies? </h4>
<p class="style2">Not if it s not necessary. Volume Shadow Copy
Services is a technology that can be used to copy files that are
locked or in exclusive use by some other application. The creation
of the snapshot is pretty fast, but there is no need to force the
system to make a shadow copy if you know that none of the files to
backup will be in use. <h4>Is it better to create separated backups
or to overwrite? </h4>
<p class="style2">It depends. Sure it is prettier to overwrite or
update a backup, and have all your files in one place, but having
separated backups (full or not) has several advantages: you can
maintain several versions of your files, for example. But the more
important thing is, that by overwriting an old backup you are taking
the risk that if the backup is corrupted, interrupted, or canceled,
you may end up having a backup in bad state, so use separated
backups when possible and then, use the automatic function for
deleting old backups.
<p class="style1"><a href="index_en.htm">Index</a></td>
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<p class="style1">⌐ 2000-2012 by Luis Cobian<br>
All rights reserved</td>
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