Question

1. For the following questions, describe in detail what happens in a RAID-5 system when one disk fails. You may assume a system with 6 disks.
   1. ( 1 point) What happens when reading a piece of data from which the parity is stored on the failed disk?
2. 2. (1 point) What happens when reading a piece of data for which the actual data is stored on the failed disk?
3. 3. (1 point) If we replace the failed disk with a new disk, how could the system be returned to its original state?
4. 4. (2 points) How much data would need to be read and written during recovery? Estimate how long recovery would take if there were no competing requests in the system.
5. 5. (2 points) What might happen if we want to write a new piece of data while there is still a failed disk in the system? List at least two options. For each option, say how this would complicate your answer to the previous question.

Answer 1

RAID 5 is a redundant array of independent disks configuration that uses disk striping with parity. Because data and parity are striped evenly across all of the disks, no single disk is a bottleneck. Striping also allows users to reconstruct data in case of a disk failure.

RAID 5 evenly balances reads and writes, and is currently one of the most commonly used RAID methods. It has more usable storage than RAID 1 and RAID 10 configurations, and provides performance equivalent to RAID 0.

RAID 5 groups have a minimum of three hard disk drives and no maximum. Because the parity data is spread across all drives, RAID 5 is considered one of the most secure RAID configurations.

The benefits of RAID 5 primarily come from its combined use of disk striping and parity. Striping is the process of storing consecutive segments of data across different storage devices, and allows for better throughput and performance. Disk striping alone does not make an array fault tolerant, however. Disk striping combined with parity provides RAID 5 with redundancy and reliability.

RAID 5 used parity instead of mirroring for data redundancy. When data is written to a RAID 5 drive, the system calculates parity and writes that parity into the drive. While mirroring maintains multiple copies of data in each volume to use in case of failure, RAID 5 can rebuild a failed drive using the parity data, which is not kept on a fixed single drive.

RAID 5 is one of the most common RAID configurations, and is ideal for application and file servers with a limited number of drives. Considered a good all-around RAID system, RAID 5 combines the better elements of efficiency and performance among the different RAID configurations.

Fast, reliable reads are major benefits. This RAID configuration also offers inexpensive data redundancy and fault tolerance. Writes tend to be slower, because of the parity data calculation, but data can be accessed and read even while a failed drive is being rebuilt. When drives fail, the RAID 5 system can read the information contained on the other drives and recreate that data, tolerating a single drive failure.

Longer rebuild times are one of the major drawbacks of RAID 5, and this delay could result in data loss. Because of its complexity, RAID 5 rebuilds can take a day or longer, depending on controller speed and work load. If another disk fails during the rebuild, then data is lost forever.

PLEASE GIVE A LIKE***