Two factors you should consider before going to configure RAID level for SQL Server Data Bases are,
- Frequency of data write operation compared to read operation
- Nature of I/O (Sequential/Random)
RAID
5 /RAID 6 can be chosen for read only Data Bases. Also these RAID
configurations are the right choice for data warehouses, or for storing data
where write latency doesn't impact overall system performance.
If
frequency of write operation is more than read operation, RAID 1+0 (RAID 10)
provides the best performance since it doesn't perform parity calculations
during write operations. Of course, RAID 1+0 arrays bring a much higher
implementation cost, since the available storage is exactly half of the configured
disks in the array. So, this RAID configuration is the right choice for OLTP
implementations of heavy-write databases.
RAID
1 can be used for the transaction log since it is written to disk sequentially.
RAID 1 or RAID 1+0 can be used for the “tempdb” database files since it is a
write heavy database.
In
addition, the following points need to be considered,
- NTFS format allocation unit sizes should be 64 K (it is 4 K by default) for database data files which perform better than 4K size.
- Place data and log files on separate, dedicated disks, and making special consideration for the “tempdb” database.
- For highly transactional databases, the transaction log for each database should be located on dedicated physical disks to avoid write I/O bottlenecks.
- Since “tempdb” is used for temporary storage only, Solid State Disks can be used to significantly improve the I/O characteristics.
