Inside your PC is probably a single hard drive. It may be partitioned into a couple or more sections but it’s still one single physical drive. If this drive fails you can lose all the data on that device. Not a good place to be in. A little known fact is that hard drives have minor failures all the time,a sector will fail but the drive can detect when this is about to happen and swap it out for a good sector on the fly.
This is why backups are so important. However running backups can be missed,take time to do and generally happen infrequently. If the data on your drive is of great value or you want a performance improvement you may want to consider setting up a RAID system.
RAID stands for Redundant Array of Inexpensive Disks or Redundant Array of Independent Disks. This is a method of using multiple drives to store your data. The way the data is stored depends on the raid system,these come in the form of numbers;0,1,5,6,10 &50 etc. We will take a look at the differences in a moment.
Each RAID system has a minimum number of drives required to run and has various Space Efficiencies (SE) which is a figure from 0 to 1. 1 being 100% of the drive 0.5 being 50%,0.66 being 66% etc.
Possibly more important is the Fault Tolerance (FT) which is how many drives can fail without loss of data. Depending on how safe you want your data to be and how much budget you have for hard drives (and physical space in your PC,however you can set up an external RAID system) will have a bearing on what system you opt for. So what are the option and their advantages and disadvantages?
RAID 0
(Min Drives = 2,SE=1,FT=0)
RAID 0 is a bit of an oxymoron as it does not offer any redundancy. It simply links a cluster of drives together as one drive. So if you have three 120 Gig drives in RAID 0 your PC treats them as one large 360 Gig drive. None of the data stored on these drives has any redundancy.
On the surface of it you could argue ‘What’s the point?’. The only real advantage is that as data is spread across multiple drives the read and write times are faster. This is achieved as each block of data,generally64KB in size,is sequentiality written across each drive in the array. So when you save your file it is distributed across the drives. This system can be used where speed of access is more important than security of the data.
This setup has the maximum space efficiency of 1. With three 120 Gig drives you get to store all possible 360 Gigs of data. However if any one drive should fail you are in trouble.
RAID 1
(Min Drives = 2,SE=0.5,FT=1)
This system requires two drives and mirrors all the data between them. So if you have two 120 Gig drives they each have the same data on them. Therefore any single drive failure is recoverable.
This also helps read speeds (as in RAID 0) as data can be read from drive A whilst drive B is sent to get the next bit of data. Write speeds are however slightly slower as it has to write each bit of data twice.
The space efficiency for this system is 1/n (where ‘n’is the number of drives used). So with two drives you get a space efficiency of 0.5. ie half of the total storage is available,the other half is backup.
The fault tolerance is n-1. In this case 1 or 1 disk.
So in summary with RAID 1 you get 100% backup with a 50% reduction in useable drive space.
RAID 5
(Min Drives = 3,SE=0.66),FT=1)
RAID 5 uses a minimum of 3 drives in the array. We now have parity being stored as well as raw data. Just like RAID 1;any single drive can fail and the data is still safe.
Space efficency is 1-(1/n),so with 3 drives this is 0.66
Fault tolerance is 1 disk.
So unlike RAID 1 this RAID 5 system gives you slightly more usable space,but does require an extra drive.
RAID 6
(Min Drives = 4,SE=0.5,FT=2)
In many respects this works in the same way as RAID 5 but with dual parity blocks for each data block. This level gives you a fault tolerance of 2 disks. So is very reliable indeed. It has a space efficeny of 1-(2/n). On the minimum setup of 4 drives this is an SE of 0.5.
There are many more RAID setups but the above ones are probably the most common. Although RAID systems offer varying degrees of protection against data loss,it is still not a true replacement for backups. I like to backup all my important data to DVDs once a month,these disks are then archived in a safe location. I know the data cannot be accidentaly erased and are not effected by electromagnetism or damp etc.
However having RAID 1 or higher on your PC does make your data safer and faster to access. Now that most modern motherboards support RAID and with the price of drives so low it makes sense to implement.
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