Hello Folks,
You might have heard about this. Well I will be going to give some illustrations on it:
RAID is an acronym for Redundant Array of Independent/Inexpensive Disks. It is a category of disk drives that utilizes two or more drives in combination for increased performance and fault tolerance. RAID applications are typically found in high-performance disk systems utilized by servers to improve the persistence and availability of data.
So the different levels of RAID are:
JBOD (Just a Bunch of Disks):
- JBOD isn’t an official RAID setup, but most RAID setups offer it as an option.
- As by the name each extra disk extends the storage as if the disk is replaced with a larger one.
- It provides no fault tolerance, nor does it provide any improvements in performance compared to the independent use of its constituent drives.
- It provides two advantages to it over RAID 0:
- It avoids drive wastage.
- It has easier disaster recovery.
- Redundancy Percentage (Percent of disks dedicated to redundancy) is 0%.
RAID 0:
- It offers data striping in which the data is spread out across multiple drives, speeding up data writes and reads.
- There is no parity, redundancy, or fault tolerance.
- This RAID level offers a very high level of performance compared to the other RAID levels.
- It also offers the lowest cost per megabyte.
- A minimum of two hard disk drives are required, and you can have as many drives in the RAID 0 array as are supported by the RAID controller card.
- The Redundancy Percentage is being set to 0%.
RAID 1:
- It refers to the Data Mirroring, in which data is written to the two drives and read from either of the drive, providing better fault tolerance, since if one drive fails, the other drive still has the data to keep the system going.
- It is easy to rebuild a degraded RAID 1 array, as the data is available on the remaining drive.
- In most of the RAID setups, RAID 1 will increase the read speed but will slightly decrease the write speed.
- The Redundancy Percentage is being set to 50%.
RAID 5:
- It offers Data Striping with a parity bit written to one of the drives.
- The RAID 5 parity is used for fault tolerance, i.e. If one of the disk drives in the RAID 5 array goes down, data can be recovered from the remaining drives.
- If anyone disk drives goes down then the RAID 5 array is said to be “degraded”. A degraded RAID 5 array is not fault tolerant until the failed drive is replaced and the RAID 5 array is rebuilt.
- RAID 5 is more efficient than RAID 1 when it comes to data storage. RAID 5 uses just one disk in the array for redundancy. So the more drives in the array the more efficient the array becomes.
- RAID five has slower write speeds than RAID 1, but read speeds are often increased.
- The Redundancy Percentage is being calculated by using the formula: 1/ (n-1), where n here is a number of drives.
RAID 6:
- RAID 6 is being similar to RAID 5, except the parity is being mirrored to two drives, so any data drive and one of the parity drives could fail simultaneously and the drive subsystem could continue to function.
- RAID 6 requires at least 4 drives to operate and will continue to work even if two drives are missing.
- RAID 6 is best used for mission critical applications.
- The greater the total number of drives the more efficient the array becomes.
- The Redundancy Percentage is calculated by using the formula: 2/ (n-2), where n here is a number of drives.
RAID 10:
- RAID 10 is a combination of RAID 0 and RAID 1. This offers the speed of data striping and the protection of data mirroring, where the drives are striped first and mirrored.
- RAID 10 array can sustain multiple drive failures, but only if the right drives fail.
- The performance is very good with RAID 10 arrays, and redundancy is very high, but it comes at the cost of additional disk drives.
- The Redundancy Percentage is being set to 50%.
Hope you got it understood well 🙂
And also comments on this!!
Regards
Piyush Bajaj
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Fail…. If you are going to provide RAID levels to be used on SQL servers, please be inclusive of all RAID levels. This includses those that people may not even know exist, which I assume you are one of those. RAID 5E, 5EE, 1E, 10E, 6E, 3, 4 and 4E. Basically, what you have done is said: “There are white, black and hispanics living in the US. We know there are a LOT more diverse cultures out there, but since they the minority, we will just leave them out of the report.” If you are going to publish, do your research first.
Well Draco,
Yes you are right that i am still learning and didn’t knew about this like many of us. And i am more than a happy that you have shared this information with us and devoted your precious time.
As you should know that it’s almost impossible to publish an article with full knowledge of it (although we try our best), untill and unless we also become the part of that technology. That’s why these comment boxes are meant to, to get the knowledge more resourcefully from a person like you, who wants to share the useful information, that normal human being are unaware of.
But i will sure research more on this and will publish soon on the RAID “levels” which i may had left…..well thanx…. 🙂
At last i want to say that – “I am in a learning phase and will be till my journey goes, beacause the research and development had no ends…”
Thanks peeyush,
Nice article. How can I know which RAID level is implemented on server(Or it is implemented or not)? Do we need to take additional steps(at programming,installation or configuration) so that SQL server can utilize RAID provided by storage system? I assume it is done automatically.
Thanks,Naveen
Hi Naveen,
To find the RAID level implemented, you need to get in touch with the storage\server admin, probably you’ll not have the access to check those things yourself.
There is no configuration required on SQL Server in order to make use of RAID.
RAID is something which gets implemented on Storage level, there are two RAID implementation types, H\w Level RAID, Software RAID. we are reffering to H\w based RAID which gets configured on Storage\ SAN\ NAS. Now It doesn’t matter what exactly you put on these drives\mount points, be it files\ SQL Server files etc, these will make use of configured RAID, No seperate software configuration is required for this.
Thanks,
Sarabpreet Singh
You have to setup a SQL server and specify the disk layout. SAN Storage have given you RAID01, RAID1, RAID5, RAID10. How will you configure the drives for SQL?