subject: How to Choose the Right RAID Level for your Array [print this page] How to Choose the Right RAID Level for your Array
There is a wide range of different RAID configurations that are commonly used today and each has its advantages and disadvantages, depending on the application for which you use them. In this article, we'll discuss what you should look for in a RAID array, some of the more common RAID setups and the positives and negatives of each choice.
What to look for in a RAID array
There is no one level of RAID that will best suit every application. The choice depends on your situation and priorities. There are four main areas you should consider, performance, capacity, availability and cost.
Performance:
The most important thing is to choose a RAID level that matches the workload of your system. Some applications require very fast data transfer while others work just as well at a lower rate.
Capacity:
The various RAID levels all have different amounts of storage space available after enough capacity has been set aside for the actual RAID operations. Different RAID levels offer different storage capacity levels and this will have a significant impact on choosing the right level.
Availability:
In some cases your main concern when choosing a level will be based on system availability. Business users who cannot afford to have the system down for any length of time require a RAID level that puts a premium on availability.
Cost:
In a perfect world we wouldn't have to worry about cost, but of course, this can be a significant factor that affects our choice of data array. Both high performance and high storage capacity come at an increased price and in the real world you may have to analyze the trade-off and make tough decisions.
Common RAID levels and how they stack up
For the purposes of this article, we'll look at a few of the most common RAID levels and how they compare on the four key components. Keep in mind that RAID 10 is a nested version of RAID 1 and 0 and the same applies for RAID 50 and 60 as well.
RAID 0:
Raid 0 has the best performance of any of the levels since there is no overhead or storage capacity that is strictly allocated to the maintenance of the array. You also get 100% utilization of the disk since there is no mirroring or parity information to be stored.
The big disadvantage of RAID 0 is the availability. If any disk in the array fails, all of your data is lost. There is no data protection capability at all.
When it comes to cost, RAID 0 is by far the cheapest of the available options.
RAID 1/10:
RAID 10 allows data to be read from more than one disk at a time and gives you outstanding performance. RAID 1 or 10 are both good choices when performance is high on your list of requirements.
Capacity is a downside of RAID 1/10. Due to the need to keep an identical mirrored copy of all data stored on the array, the storage capacity of a RAID 10 array is only half of a RAID 0, given disks of the same storage capacity.
On the other hand, RAID 10 provides excellent availability, you could potentially lose multiple disks without losing your data. The cost of a RAID 10 array is fairly high when compared to the amount of storage capacity you get, but it does give you a fairly high performance level for the money.
RAID 5/50:
Raid 5/50 gives you excellent performance for reading data, but a relatively poor performance when it comes to writing data, due to the need to write parity information on the drive along with the actual data. RAID 5/50 is excellent in the capacity department, losing only 33% of its raw capacity to overhead.
The availability of RAID 5/50 is reasonable but not great. RAID 5 configurations can lose one disk without losing data, while RAID 50 can lose as much as one disk in every sub array without losing data. RAID 5/50 is a bit more expensive than RAID 0 but is otherwise the cheapest of the options in this article.
RAID 6/60:
RAID 6/60 offers very good read performance, but even poorer write performance than RAID 5/50 due to the dual parity requirements. RAID 6 has greater capacity overhead than RAID 5, with 50% of the disk space going to overhead.
RAID 6/60 provides excellent availability, allowing you to lose as many as two disks in each array and continue to function. In terms of cost, RAID 6/60 is the most expensive of the options here.
As a general rule, RAID 50 offers the best storage capacity, RAID 10 the best performance and RAID 6/60 offers the best data protection. Choosing the right RAID level will match the functionality you need with the data security that you need. The choice is yours. Remember that choosing the correct RAID for your business could minimize the chances of lost data saving you money when it comes to lost business, as well as reducing the chance that you'll need the services of a data recovery firm to help you get back online.
