Page updated 5 September 2008
We hear a lot about backing up the data on our computers. Why do we need to? Well if you only use your computer to browse the internet, use webmail (e.g. Hotmail) to access all your email, and never use the computer to write important documents then perhaps you don't need to.
If you are a normal computer user then you use it every day, and it continues to work, and you don't give it a moment's thought...
... until it is too late!
We start with a description of what disk drives are and how they work and llok at why they might stop.
We will then look at ways you can take steps to protect yourself.
Computers store data on disk drives. These are marvels of mechanical engineering. They store data on flat disks or platters. These disks spin round and record/read heads are moved over the surface from the outer edge to the centre and can read and write data written on magnetic particles on the disk surface. Magnetic signals, representing the data, are only read when the recording medium is moving relative to the read head. If you can visualise it the head will read data from a circular path around the disk. This is called a track. When the drive moves the head towards, or away from the centre of the disk further tracks can be read.
Disk platters have two surfaces and both can be used for recording. There is a second read/write head on the other side but usually the heads move together.
Many drives have more than one platter so you can have multiple heads reading several tracks at once. These tracks are sometimes referred to as cylinders as they form concentric sets of tracks one above the other.
If the head was in contact with the disk then it would wear the surface. This technique is used on floppy disk drives (remember them!) as the media is disposable and compared with the hard disk drives (HDD) we are talking bout here rotate very slowly. On HDDs these the heads "fly" just above the surface. As the disk rotates at it carries a film of air around and this creates an air flow (called a laminar flow) that is used to keep the head a tiny distance above the surface. This flying distance is about 0.5 millionths of an inch a human hair is around 4000 times that! Dust particles on that scale are enormous.
A few moments thought will lead to the realisation that the surface must be incredibly smooth for a head to maintain that distance. There must be no chance of dust getting into the drive enclosure which is why all modern disc drives are sealed. Vibration also has to be taken into account to make sure that the heads remain flying. If the do touch the surface then the dalsoisk surface (and the head) are almost certain to be damaged.
Here is a more detailed description of matters related to disk drives - click this link
The disk drive is made these days in two main sizes, 3.5 inches, 2.5 inches. Smaller sizes are made, typically for niche markets.
The faster the rotational speed the faster data is transfered and the quicker the part of the disk you are waiting for will come past the reading head.
Another factor affecting performance is how fast the heads move across the disk. This is measued in milliseconds. From a performance point of view the faster the better.
Disk capacity depends on:
Putting this all together - the disc drive is a miracle of modern engineering. To manufacture such drives is a precision engineering task and the surface coating of the platters is a triumph of chemistry and physics. 20 years ago a 500 megabyte drive was the size of a washing machine and cost thousands on pounds. Today 1000 gigabytes are packed into a 3.5 inch drive. The prices of these drives are falling steadily and the capacity of the drives increases year on year. ! Terabyte costs around £100 today.
Reliability is also very much better than it used to be with figures or 500,000 hours Mean Time Between Failures being typical.No wonder we tend to ignore them!
Disk drives are mechanical devices,
There are external factors than can damage drives or at least the data recorded on them
Disk drives have imperfect coatings. The densities are such that there are always a few manufacturing defects. Disk drives detect that the surface is flawed and mark that area as being unusable and internally map that area to another part of the disk. A marginal area of the disk therefore may slowly deteriorate and eventually start showing errors. These can be "repaired" by marking the disk as being unusable but a vital bit of data was in the now faulty area it is lost for ever.
This type of failure will show up are random data errors, sometimes the operating system will recover from such errors, it can read blocks of data it has just written, detect that the data was not written incorrectly, mark the area as being flawed and rewrite the data. The Event logs may show errors.
With this type of failure it is usually possible to read (most of) the data and copy to another drive.
The second type of failure is more catastrophic. the heads make contact with the disk surface damaging the surface or the head. The disk becomes unusable and often makes a clicking noise. the computer will not boot.
With this type of failure recovery of data may still be possible but is EXPENSIVE. No data can be recovered aYest home and recovery requires specialist equipment.Typical prices are in excess of £300. Although high success rates are claimed nothing can be guaranteed.
Disks are reliable but they do fail. Some drives seem to be more reliable than others - search the web for any reports. Unfortunately much of this information is based on personal experience of a few drives. I am not sharing my own experience on these pages as the sample is too small.
There is almost nothing you can do to prevent failure. It is often not predictable. when it happens it is always inconvenient and can be traumatic. I was backing up my computers but not as regularly as I should. I received a phone call from a friend with a problem. She had taken a large number of important family photographs on her digital camera and transferred them to her computer. She deleted them from her camera and went to bed. She left the computer on as there was a problem with the power switch.
When she went to the computer the next day there was a BSOD (Blue Screen of Death) showing. she tried rebooting the computer and it would not boot and there was a clicking noise. I had a plea for help. I was able to recover the deleted photos from her camera (but not all from her partner's camera) but the disk was totally dead. She had no backup!
It took her experience to provoke me improve my own backup regime, something I had been meaning to do but never quite got round to.
This is now working and about two weeks later one of our laptops started displaying evidence of a dying disk drive. We had had two earlier spells of disk errors that had apparently gone away. In other words the Operating System had recovered the data and marked the areas as being unusable. I replaced the disk and rebuilt the laptop and was able to recover all the data.
I have three computers in the house. My wife has a laptop she uses for email and correspondence, I have a laptop used (these days) for experimentation. I also have a desktop used for my email and correspondence. This also tends to be the repository for documents which have been accumulating since we first had a PC. I have a wireless network which links the laptops to my desktop and the Internet.
The lesson for me was that backing up to DVD (one of my previous approaches) required the disk to be inserted and the backup software to be manually started. This was always put off until another day.
Using a USB hard drive is quicker but now you have to get the drive from wherever it is kept, plug it in and then run the software. Moving this between machines proved to be inconvenient at is was also used for other things.
I did however experiment with backup software, especially Syncback, which although it is very good has one problem. When programs like Outlook Express were running your email could not be backed up. This made the backup more complex as you had to remember to shut down all programs that were running while the backup was taking place. The paid for version of Syncback avoided this issue by using Volume Shadow Copy, a feature of Windows XP and Vista, that does permit open files to be copied. This feature is not in the free version of Syncback.
There are two alternative strategies for backing up computers
These both have merits and are not mutually exclusive.
I look for freeware solutions for home use wherever possible
I had already looked for alternative software packages and had already found a program called Cobian before my friend had her disaster. I was experimenting with backing up a laptop to the desktop computer. Cobian can run on a schedule which avoids the amnesia problem but of course the desktop computer has to be powered on.
Cobian has the following features which attracted me to it and this program is now my recommendation over Syncback.
Cobian is not perfect and I have two (relatively minor) issues.
It seems to work well.
The market lead has always be Norton (now Symantec) Ghost and this is an excellent program. I have been using a version of it for years. The more recent versions can take a copy of a running machine and then take incremental backups as the disk sector level. There are competitors however which have an equally good reputation.
I can see advantages of this approach in that the whole disk is backed up makin restoration easy in the case of disk failure. It is however perhaps harder to understand how to configure, and errors in configuration or making changes to where the data is stored can lead to a false sense of security as the full backup can be deleted and therfore the incremental changes that depend on it are worthless.
I am adopting drive backup as part of my backup regime but pan to do this manually rather than on a schedule. I have found a freeware package which seems to perform this function well. DriveimageXML.
This program can
The table below compares Cobian with DriveimageXML. Ghost and Syncback have also been included for comparison
|Type of software||Freeware||Freeware (commercial version also available)||Freeware||Commercial|
|Supports Full drive backup||Not really||No||Yes||Yes|
|Supports full drive restore to a new drive||No||No||Yes - but needs disk partition to be created with other software first||Yes - may need partitioning first|
|Supports Incremental Backup||Yes||No||No||Yes|
|Supports Backup cycle (see individual page for more details)||Yes||No||No||Yes|
|Backs up open files||Yes||No (commercial version can)||Yes||Yes|
|Scheduled backup||Yes||Not known||Supports interface to Windows Task Scheduler||Yes|
|Recover individual files||Yes
(using Windows Explorer)
|Recover complete folders||Yes
(using Windows Explorer)
|Time taken for backup (depends on size of data)||1-30 mins||Not known||2-3 hours||Not known|
A number of options exist for storing backups. Any of them can be used for file based backup. Full drive backup needs a storage device big enough to hold all the data or the software must support spanning across multiple devices.
In general it is much more convenient if one backup "job" fits onto a single disk.
The alternatives available are summarised in the following table.
|CD RW||640-700 Mbyte||Probably too small to be of much use today|
|DVD RW||4.7 Gbyte
9.5 Gbyte (double sided)
25+ Gbyte (Bluray - expensive)
Viable for backup of My documents and Email. Standard DVDs may be too small for large collections of photographs
|USB memory stick||2-8 Gbyte (or more)||
Probably too small at affordable sizes.
Some memory sticks are slow. I have two USB sticks purporting to be USB 2. One of which transfers data at 40 times the other.
|USB Hard Drive||Yes40 gbyte to 1 terabyte||
Viable for both file and disk options.
Larger and faster drives need an external power supply. Need to be plugged in before backup can take palce
|Another computer||Whatever is left over||
Viable if there is a common local area network connecting two or more computers together
Both machines have to be on to take a backup
PCs use more power than dedicated storage solutions for leaving on permanently
|A Network Storage device||500 gbyte upwards - how much can you afford?||
A dedicated storage solution. Some are suffiently low power to leave on permanently.
Some models provide resilient disk storage to further protect against component failure.
The choice of storage solution depends on your requirements. It is a trade-off between cost and convenience. I opted for a Network Storage Device, otherwise known as a Network Attached Storage (NAS) device.
The description of backup software however does not depend on which technology is chosen.
I realised that an independent storage device connected to my network might be the answer if it was affordable. Such devices are called Network Attached Storage. This would have the benefit, compared to a USB device, of being accessible to all computers on my network
The criteria for such a device - my wish list - was as follows
My "Goldilocks" device is the ICY Box IB-NAS4220B device. It is available from several suppliers. I bought mine from DABSI have added some pages which describe how to set up and configure the box. The introductory page can be found here