A backup, in computer lingo, refers to making a copy of
important data for the purpose of data recovery. Should
the important data get damaged or lost, a properly made
backup will restore it all. The word "data" refers to
anything stored on a computer system: images, programs,
document, videos, etc. Taking backups of important data
can prevent loss of valuable work and the time needed
to recreate it.
In this article we'll take a look at common backup types
and strategies, data compression, and common backup media
types. A real life backup scenario will illustrate my
own backup procedures. The article will end with general
backup tips.
COMMON BACKUP TYPES
The best backup methods rely on simple and time proven
concepts. New or unnecessary technologies are best
avoided till proven reliable and necessary. The simpler
the procedure, the more likely it is to work correctly.
A full-backup consist of making a copy of all important
data. When you copy a folder with important files,
from say a hard drive to a floppy, you actually make
a full-backup of those files. Due to simplicity,
this approach is the most reliable of all backup
types. Its main advantage is ease of backup creation
and restoration. The main disadvantage is that the
backup will use as much space as the important data. If
the data is large, the backup process can be very
resource intensive in terms of time and the processing
power needed to carry out. Imagine the time needed to
full-backup a digital library consisting of millions of
books. Such operation takes days.
An incremental-backup works differently in that it backs
up only the modified files since the last backup. When
using this method, a full backup is created first and
then incremental backups are run on regular basis. For
large amounts of data this method is often the only
practical way to backup. It takes up less space than a
full backup and is less resource intensive to run. On
the other hand, contrary to full backups, incremental
backups need dedicated backup software to keep track of
what files to backup.
Compressing the backup data is a popular option. Such
practice lowers the amount of space needed on the backup
media. Although compression adds an additional layer
of complexity, it can be a good (if relied on wisely)
and sometimes necessary solution.
ESSENTIAL BACKUP STRATEGIES
Regardless of the backup type and data, the following
backup strategies should always be followed:
backup should be taken on a regular basis
backup should be automatic and need as little human supervision as possible
backup should be stored in a safe remote location
backup should rely on well established hardware and software technologies
Backup should be taken on a regular basis. The more
frequently the data changes the more often it should
be backed-up. For example, some of my most frequently
updated files (website files, source code, notes,
etc.) are backed-up daily. Files that are less
frequently updated are backed-up monthly.
Backup should be automatic. Except for the initial
configuration of the backup program and the occasional
supervision, the whole backup process should be automatic
and completely transparent. That is, the backup should
run by itself without causing any attention unless
necessary.
Backup should be stored in a safe remote location. Should
the location of the important data get damaged,
destroyed, or exposed to theft - a remotely stored backup
becomes invaluable. How remote? Disasters like fire,
flood, tornado, earthquake, etc., can cause widespread
damage. Ideally a backup should be stored in a far away
enough, minimal risk location.
Backup should rely on well established hardware and
software technologies. Such technologies are typically in
widespread use - thus cheaper and easier to troubleshoot,
or get help in the event of failure. As established
technologies become gradually replaced by new and
better ones, so should the backup media and hardware
and, if used, the software to re/store the data. There
is no guarantee that the common backup media of today,
like CD or DVD, will be usable in ten years. The same
is true for software. A good data preservation strategy
should include continual migration of the backup data
to mature and well established technologies of the time.
A BIT ABOUT DATA COMPRESSION
Compression makes data smaller and thus is a popular
backup option. Its main advantage is lower backup
cost due to lower space use. The downside is the time
needed to compress the data and later to uncompress it
for restoration.
Many compression formats exist. Each format use some
sort of compression method called an algorithm. There
are two types of data compression algorithms: "lossy"
and "lossless". Lossless compression reduce the data
size without modifying its content. Lossy compression
modify the data content to make it even smaller than
lossless compression.
Some compression formats, like MP3 or JPG, are highly
specialized. They use lossy algorithms and produce very
small file sizes but can only compress a particular
type of data. Other formats, like ZIP or BZIP2, are
of general purpose. They rely on lossless compression
algorithms and can work on any data. However, they will
never outdo special purpose formats like MP3 or JPG.
PNG and TIFF are popular image file formats which support
lossless compression.
Unfortunately, due to the nature of lossy compression,
JPG, MP3 or any other lossy format degrade the original
data to some extent. In other words, saving an image or
music in a lossy file format will make it different then
the original. Usually the difference, called compression
artifacts, is so small that most of us don't see or
hear it.
For the above reasons, lossy compression should never
be used when saving important data. Only lossless
compression is suitable for that. PNG and TIFF are
examples of image file formats that support lossless
compression. Such formats are ideal for storing
hi-resolution master images.
Finally, compression takes time and normally uses all
available processing power. Generally, the better the
compression the slower it is. Some compression algorithms
are extremely good at compressing but also extremely
slow. For backup purposes, one should evaluate common
compression formats and set for the most suitable one.
CONSIDER YOUR NEEDS
Some additional issues need to be considered when
designing the most suitable backup strategy for own use:
the type of backup files
if compression is desired, what compression to use and how
backup storage media
As noted earlier the best backups are simply copies of
important data. Such approach works especially well for
artists who rely on compressed image formats like PNG
or TIFF.
Note the difference between "built-in" image compression,
done every time you save an image in a format that
supports it, and compressing the backup data - applied
to all backup data regardless of what it is.
What backup compression to use, and if to use it at all,
depends on the type of backup data. Generally,
text files (TXT, HTML, XML, etc) can be compressed
the most of all file types. Images that have been
compressed with their own algorithms (PNG, JPG, TIFF,
etc) can't later be compressed much if at all. Images
which don't have own compression (BMP, TGA, etc) can
often be compressed quite a bit, though this depends on
the actual image data.
Thus if most of your important art data consist of
images that are already compressed, there is no need to
compress the backup. Text files on the other hand, can
be compressed a lot and save significant amount of space.
There are a few other things to consider when compressing
backup data. What compression program to use and how
to compress the files.
ZIP is the most commonly used compression format today -
it's fast and compresses well. It's been around for a
long time and is universally available. But there are
other, less known, good alternatives. For example,
7ZIP, RAR, and BZIP2 compress significantly better than
ZIP and are only slightly slower.
Finally, how to compress backups. Basically one can
either create a compressed archive of many files, or
compress each file individually. The main disadvantage
to creating a compressed archive is the possibility
of losing all files in the archive if the archive
gets corrupted and can not be recovered. On the
other hand, if files are compressed individually one
looses only one file - should it get corrupted and be
unrecoverable. Additionally, since a compressed file
use less space than uncompressed, it's less likely to
get corrupted. Thus it's more safe to compress files
individually.
WHICH BACKUP MEDIA TO USE
The commonly used backup media today are hard drives,
tapes and CDs/DVDs. Hard drives are the fastest and
often the best option for large amounts of data. They are
also the most expensive and not very durable. Tapes are
slow but can store a lot of data and can last decades.
CDs/DVDs are probably the most common backup media used
today due to its very low cost. Unfortunately, just
like hard drives, most have a relatively short expected
life span of between two to five years. Internet backup
solutions are also becoming a popular backup option.
Reliability is important to consider when choosing the
backup media. How robust is the media and for how long
can it retain the data? The quality of the media plays
a significant role here. All media degrade over time,
but some degrade more than other. Most of the low cost
burnable CDs have a life span of around two years. Higher
quality CDs can last up to five. Very high quality
CDs with a gold layer are expected to last decades.
Generally, if the handling and storage conditions
are good, quality media should last at least few years
without data loss. However, unless the best quality media
is used, an annual full backup is probably the safest
prevention against data loss due to media degradation.
A combination of different media may often be the ideal
solution. For example, some of my own backup practices
include using an external hard drive to mirror (update)
certain parts of my computer hard drives. Twice a year
I burn all important data on several DVDs.
I recommend spending some time investigating the most
suitable media and the hardware to operate it. High
quality products will minimize the possibility of
backup failure.
THE NECESSITY OF VERIFYING BACKUPS
The most important aspect of taking backups is making
sure they are error free. The backup data may prove
useless if corrupted due to media or other error.
It's good practice to immediately test the backup for
its validity. Errors will be detected and a new backup
can be taken right away. Any respectable backup program
provides an option for data verification. What good is
a backup if its data is corrupted?
A REAL LIFE BACKUP SCENARIO
My most valuable data is my art data, website files,
source code, and various docs. All my hi-resolution work
is stored in either PNG or TIFF. Nearly all my reference
images are JPGs. Thus all my image data can be backed
up without the use of compression and save huge amounts
of backup time and space. I do compress 3d files which
don't use own compression. For that I use bzip2 with the
maximum compression setting. All the remaining data are
basically text files and are compressed individually
using either bzip2 or 7zip. Images and 3d files, even
compressed, can be huge in size. Not surprisingly over
90% of my backup space is used on art data.
I backup daily, monthly and twice a year. Once a day,
the files which are frequently updated (notes, work
in progress images, source code, website files, email,
etc.) are backed up to another hard drive. This happens
during the boot process and takes a few minutes. Once
a month I backup to a CD which also includes less
frequently updated files. A copy of that CD is stored
in a remote location. Twice a year I take full backup
and store it on several DVDs at a friends house. If I
work on something especially important, I store it daily
on a CD/DVD or a USB mem-stick. My most critical data
is also regularly encrypted and stored on a very remote
internet host. I wrote a script to run all these backups
automatically. With the exception of CD/DVD storage,
no manual work is involved.
As you can see, a custom backup solution can be quite
sophisticated yet simple to carry out. It can involve
a combination of different media and backup procedures
to optimally satisfy ones needs.
FINAL NOTES
Depending on your needs a dedicated backup software may
be a necessary investment. Make sure to research this
carefully. Usually, products from reputable companies
that specialize in certain solutions are best. There are
also many good open source or free software alternatives.
It's best to avoid products which rely on proprietary
or closed solutions. For example, a backup software
may store the backup data in an unknown format only
supported by this particular backup software. Avoid
that. If the company goes out of business and the
backup software breaks, your backup data may be lost
forever. Look for products that rely on well known,
mature, and ideally open technologies. For example,
PNG is an open format for storing image data. What this
means is that the specification, or blueprint, for that
format is publicly available for anyone to use it. This
increases compatibility and reduces reliance on any
specific vendor or product.
Most artists important data consists mainly of images
and 3d files. To save space rely on PNG, TIFF or JPG
for bitmap image formats. Vector images and 3d files
can be compressed individually if needed. A basic
backup software that simply copies specified files
or directories to the backup media may be all that
is needed. It's best to make two sets of the backup
data and store each at different location. One close
to home, like a friends place, or a bank box and the
other far away.
Setting up a proper backup strategy may initially require
a significant amount of time and cost money. There is
a lot to research and consider. In the end however,
a good backup procedure will prove an exceptionally
valuable investment. As you read this, your screen could
go blank due to a hard drive crash. All your valuable
data - years of work, reference images, documents,
photo albums, 3d files, email, etc., - could be lost
forever. Unless you were prepared and took a backup.
Dawid Michalczyk is a freelance illustrator and an artist. He has been creating computer graphics since the early 90s. To see examples of his work and other writings visit his website at http://www.art.eonworks.com. He can be reached at dm@eonworks.com
No comments:
Post a Comment