RAID
RAID
Introduction
RAID (Redundant Array of Inexpensive Disks) is a way of using 2 or more Hard Disks Drives of the same size together to improve their performance and/or reliability. A group of disks using RAID are called an &array& and there are several types of array including RAID0, RAID1, RAID5 and RAID1+0. If your budget is large enough to buy more than 1 hard disk, it's worth considering the different types of RAID arrays too see if any could enhance your PC .
There are a number of different RAID &modes&, each providing varying degrees of improved performance and reliability. Choosing which RAID mode is best for you will depend on whether your priority is to improve speed, reliability or both, as well as how large your budget is. There are a number of factors that are effected by which RAID is being used:
Read speed is the time it takes for a given piece of data to be retrieved from the array.
Write speed is the time it takes for a given piece of data to be stored in the array.
Reliability is the likely hood of a given piece of data being lost due to one or more of the drives failing.
Cost is dependent on how expensive the system will be to provide a given amount of storage space.
Naturally none of the RAID array modes will score highly on every factor, but each does provide significant benefits for certain situations
.
Explanations
RAID 0 ‘The Stripe‘
The downside to this is that if just one of the drives in the array fails, all the data across the whole array will be lost. This Type of Array is best suited to situations where both read and write speeds are a priority. It should never be used to store important data.
Good for:
Operating System .
Fast Storage of unimportant data (do not use RAID 1 as primary storage space)
RAID 1 ‘The Mirror‘
RAID 1 is the simplest type of array and is used to improve reliability. It needs an even number of drives in the array and simply mirrors the data across the Array. Say you were using 2 drives, it would write the same data to both drives at once, giving you 2 copies of that data. if one drive were to fail, you would still have all the information stored on the other drive. The down side to all of this is that the cost doubles, as you will only have the storage space of one drive. So if you are using 2 x 500GB drives, you would still only have 500GB worth of storage space, as the other 500GB are being used to backup the first.
This type of array is perfect for someone looking to secure their data against HDD failure, however it will produce no performance gains.
Good for:
Reliable Storage
Operating System (if one disk goes down the system will still be usable.)
RAID 5 ‘The Stripe with Parity‘
RAID 5 is a slightly more complicated array which combines some benefits from both RAID 1 and 0. It requires 3 or more drives, using the space of one drive to improve the reliability of the array. It does this by writing a given piece of data to any 2 of the drives in the array. If one drive then fails, it can still retrieve all the data that was stored on it from the other drives in the array. The benefit of this over RAID 1 is that you only lose the space of 1 drive, rather than half the total space. So if you were using 4 disks, then with RAID 5 you still have the space of 3, as oppose to 2 with RAID 1. It does mean however that if 2 drives go at the same time, then all the data stored across the entire array will be lost.
Speed is something of a mixed bag. Read speeds are extremely good as it acts like RAID 0 array, taking parts of the data from different drives at the same time. Write speeds however are poor, because it has to work out which drives to write the copies or &parity& data to. This type of array would be good for a media or database server. It is not suited to an Operating System install because the write speeds are so low.
Good for:
Media Server
Database Server
RAID 10 ‘The Striped Mirror‘
RAID 10 is a combination of RAID 1 and RAID 0. Essentially it is like having a striped array, which is then mirrored to give improved reliability. The primary benefits to this system are that firstly you get the performance of a RAID 0, with the reliability of a RAID 1. It can even survive multiple disk failures, provided they are not both on the same side of the stripe. The downside to this setup is cost, as it requires at least 4 drives but will only provide the storage space of 2. The data stored on the array will only be lost if 2 drives fail on opposite sides of the mirror.
Good for:
Fast, reliable storage
Operating System.
RAID 0 ‘The Stripe‘
RAID 0 is used to improve performance of both Read and Write speeds using 2 or more HDDs. It does this by splitting the work between the available disks in &stripes&. So for example, say you have 2 HDD, it will write half the data to one drive and the other half to the second drive. This (theoretically) doubles the performance of both read and write speeds. In reality the average performance gain is less than that, but still marks a significant improvement over a single drive, particularly when moving large amounts of data around.
The downside to this is that if just one of the drives in the array fails, all the data across the whole array will be lost. This Type of Array is best suited to situations where both read and write speeds are a priority. It should never be used to store important data.
Good for:
Operating System .
Fast Storage of unimportant data (do not use RAID 1 as primary storage space)
RAID 1 ‘The Mirror‘
RAID 1 is the simplest type of array and is used to improve reliability. It needs an even number of drives in the array and simply mirrors the data across the Array. Say you were using 2 drives, it would write the same data to both drives at once, giving you 2 copies of that data. if one drive were to fail, you would still have all the information stored on the other drive. The down side to all of this is that the cost doubles, as you will only have the storage space of one drive. So if you are using 2 x 500GB drives, you would still only have 500GB worth of storage space, as the other 500GB are being used to backup the first.
This type of array is perfect for someone looking to secure their data against HDD failure, however it will produce no performance gains.
Good for:
Reliable Storage
Operating System (if one disk goes down the system will still be usable.)
RAID 5 ‘The Stripe with Parity‘
RAID 5 is a slightly more complicated array which combines some benefits from both RAID 1 and 0. It requires 3 or more drives, using the space of one drive to improve the reliability of the array. It does this by writing a given piece of data to any 2 of the drives in the array. If one drive then fails, it can still retrieve all the data that was stored on it from the other drives in the array. The benefit of this over RAID 1 is that you only lose the space of 1 drive, rather than half the total space. So if you were using 4 disks, then with RAID 5 you still have the space of 3, as oppose to 2 with RAID 1. It does mean however that if 2 drives go at the same time, then all the data stored across the entire array will be lost.
Speed is something of a mixed bag. Read speeds are extremely good as it acts like RAID 0 array, taking parts of the data from different drives at the same time. Write speeds however are poor, because it has to work out which drives to write the copies or &parity& data to. This type of array would be good for a media or database server. It is not suited to an Operating System install because the write speeds are so low.
Good for:
Media Server
Database Server
RAID 10 ‘The Striped Mirror‘
Good for:
Fast, reliable storage
Operating System.
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