RAID, RAID, RAID, you just can't get enough.

When I first heard about RAID technology in my IT 305 class I didn’t know what to think at all. It was somewhat of a in one ear out the other kind of thing to me since it was extremely boring. After a couple weeks I actually began reading and started to understand it somewhat. RAID stands for Redundant Array of Independent Disks. The purpose of RAID is to improve the functionality and cost of storing your data. There are 6 different kinds of RAID not including Nested which is combinations of different kinds. The different kinds and a little description are,

RAID 0     Striped array with no fault tolerance

RAID 1     Disk mirroring

RAID 3     parallel access arrays with dedicated parity disk

RAID 4     Striped array with independent disks and a dedicated parity disk

RAID 5     Striped array with independent disks and distributed parity

RAID 6     Striped array with independent disks and dual distributed parity

Nested       Combinations of RAID levels. Example: RAID 1 + RAID 0

There are different positives and negatives to using each kind of RAID. There are also minimum requirements, kind of like when installing certain software on a computer, sometimes you may not have enough RAM and the program will not install. Same thing with RAID, if you do not have the minimum requirements then you will not be able to implement that particular kind.

RAID 0 is the cheapest form to use and it requires a minimum of 2 disks. It has a storage efficiency of 100%( which is pretty high in my opinion) and it has a very good Read and Write performance with no penalty.

RAID 1 has a high cost & it requires a minimum of 2 disks. It has a storage efficiency of 50%.( not looking so good) The Read and Write performance is good and the write penalty is moderate.

RAID 3 has a moderate cost and requires a minimum of 3 disks. The storage efficiency of it depends on how many disks are used, the higher the number the lower the efficiency. It is good for random reads and very good for sequential reads. It is poor to fair for small random writes and good for large sequential writes, the write penalty is high.

RAID 4 has a moderate cost as well and again it has a minimum of 3 disks required. The storage efficiency is dependent on the number of disks, the higher the number of disks the less efficient the storage. It is very good for random reads and good to very good for sequential writes. It is poor to fair for random writes and fair to good for sequential writes. RAID 4 also has a high write penalty.

RAID 5 has a moderate cost and needs a minimum of 3 disks. The storage efficiency depends on the number of disks, more disks are less efficient. The read performance is very good for random reads and good for sequential reads. The write performance is fair for random writes, it is slower due to parity overhead and it is fair to good for sequential writes. RAID 5 has a high write penalty.

RAID 6 has a moderate cost but it is more than RAID 5. Its storage efficiency is the lowest out of all of them and it has the highest write penalty.(ok now for some good news) The positives of RAID 6 are that it is very good for random reads and good for sequential reads as well. It is good for small random writes as well (remember it has a very high write penalty so you don’t want to be doing a lot of that.)

To wrap things up different RAID is better for different tasks and depending on what you plan on doing with or to your data you should plan accordingly if you choose to implement RAID or else you might as well not have done it.