RAID performance issues
RAID Recovery - RAID performance issues
Read and write performance
The key to the organization of RAID was protecting data by providing fault tolerance. In past two decades, however, protecting data is not the sole purpose of implementing RAID in a computer; performance has taken the front seat with some other factors such as reliability, availability and fault tolerance.
The basic job a hard disk does is of reading and writing. The process of reading and writing is minutely different but of great importance. Coming to RAID, the differences between read and write are highly profound since the disks are arranged in array following different mechanism. Basically, the difference between reading and writing under RAID is when data is written in a redundant environment, it must reach every nook and cranny where data is stored. While data is read back, the redundant information is not required to be thoroughly accessed. It can be further understood under the following aspects of RAID:
Read and write under mirroring: Read performance is far richer than that of write performance under mirroring. It happens because the data is duplicated and written to both drives. Such process is a bit slower than writing data on single disk. Conversely, while data is retrieved, the controller is designed in such a way that it is fetched from either of the disks.
Read and write under striping without parity: Raid 0 array reads and writes at the same ratio that a single hard disk would have. It happens because the disks in array ask as a single large disk.
Read and write under striping with parity: For reads it could be way faster than striping without parity. The entire array behaves similar to RAID 0 except for the fact that data is also spread on one extra drive. But, the difference is quite palpable when it comes to perform random read and random write.
The performance of read and write totally depends upon the RAID levels, especially the one that employs striping with parity or without parity. There are some applications where the ratio of read stays up to write, and just the opposite is also possible. It’s always recommended to take professional guidance before taking final decision.
