RAID : Understanding of RAID and its functionality

Understanding of RAID......Redundant Array of Indepenent Disks (RAID)
RAID is a combination of multilple disks to improve the performance and safety of the data. This can be configured using SCSI contollers. SCSI is nothing but a card which can have facility of connect multiple disks. Once configured the RAID, the data is available on ARRAY comprising the available disks. There are mainly 3 terms need to remember while working with RAID levels. Mirroring, Stripped disks and fault tolerance.

There are different RAID levels for various requirements. We can implement the actual RAID level to achieve 100% success.

RAID 0 : It distributes the data across multiple disks. The data retrieving can be faster as the data is dividing into multilpe disks. But this levels doesn't have any data safety, means if one disk fails you will loose the data automatically.

RAID 1 : Mirror the data from one disk to another. Here we have more safety, if one disk fails automatically another disks works which already has mirrored data.

RAID 3 (OR) 4 : This level requires minimum 3 disks including 2 for data distribution and 1 for fault tolerance. Here we have data safety mechanism with full performance including redundant data identification. For this level 1 dedicated disk is required to store redundant data.

RAID 5 : This level also requires 3 or more disks to protect the data in case any one disk fails. Here we dont required dedicated disk for storing redundant data, this will be stored in the combination of all disks. This level has higher data safety allows only one disks to fail. If more than one disks fails then the data will not be available on array.

RAID 6 : Similar to RAID 5, but it requires minimum 4 disks and allows to fail 2 disks. Means 2 disks can fail in this raid level, if more than 2 disks fails than the data wouldn't be available.


There are 2 more new levels introduced i.e....,

RAID 1+0 : Combination of RAID 1 + RAID 0, whatever the features having both levels can incorporate here. But in the sequence like first it mirror the data (safety) then distribute the data across drives (performance).

RAID 0+1 : Combination of RAID 0 + RAID 1, whatever the features having both levels can incorporate here. But in the sequence like first it distribute the data across drives (performance) then mirror the data (safety).


When consider to SQL Server installation mostly we can use RAID 5 for backups of the databases where it requires only 3 disks (less hardware) and high safety with high performance. If the data is too much important and your company can able to spend money like data worth's than any thing, you can suggest RAID 6 level where it comprises 4 disks with dual disk safety.

RAID 1+0 is good for installing Tempdb database where TEMPDB database requires safety of data with good performance.