RAID Levels of MS SQL Server 2008

To meet varying requirements for response time, data reliability, and performance, typically different RAID levels are used depending on how to design the SQL Server deployment.

These RAID levels are:

RAID 5: Known as Striping with Parity. The parity information is written across all disks in the array. Minimum of three disks to form a RAID 5 array are required. This RAID level offers better read/write performance as long as all disks in the RAID 5 are present. If one disk is missing, the read performance is degraded. RAID 5 stripes data across all disks in the array.

RAID 5 volume, needs to be formatted to ensure that it is usable for storing data.  By default, the allocation unit for a logical unit number (LUN) is 4096 bytes (4 KB) on an NTFS partition. When storing data with large files. For RAID 5 volume, change the allocation unit to 64 KB, which is 65536 bytes. .

RAID 0: Known as Disk Striping. This RAID level stripes the data across disks in the array, offering better throughput on the read/ write operations. However, there is no data protection offered in this RAID level. If one disk fails, the data stored on the disk will be lost.

RAID 1: Known as Disk Mirroring. Minimum of two disks to form a RAID 1 array are required. One primary disk is used for read/write operations, and the data is replicated to the second disk. This RAID level offers better read performance and fault tolerance, but slower write performance than RAID 0.

The scenario states that the database must be functional even if a drive fails in the system. To meet this goal, the operating system files must be on RAID 1. Using RAID 1, Mirror the operating system so that even if a disk fails, the operating system will function. The transaction logs should be placed on a separate

RAID 1 array. SQL Server writes data to the transaction logs and maintains serial information of all the modifications that occurred in a SQL database. The transaction log files can be used for rollback and roll forward operations from a SQL Server database. To enhance the performance of SQL databases, Place the transaction log files on a dedicated RAID 1.

Finally, the SQL Server files and filegroups should be placed on a RAID 5 array to achieve the best performance throughput.