Example: Writing data to a disk unit when its corresponding parity data is on a failed disk unit

 

This topic gives you an example of how to write data to a disk unit that has parity data on a failed disk unit. The write request from a system detects a disk failure for the disk unit that contains the corresponding parity data. The write request is to sector 2 on disk unit 4. Parity information for disk unit 4, sector 2, is on failed disk unit 3. The following actions occur:

1. A failure is detected on the disk unit that contains the parity data, disk unit 3.

2. Calculating parity information is not required because it cannot write to parity sector 2 of disk unit 3. Therefore, there is no requirement to read the original data and the parity information.

3. Data is written to disk unit 4, sector 2.

   A write operation requires only one write operation for the new data. Parity data for parity sector 2 on disk unit 3 will be rebuilt during synchronization after disk unit 3 is replaced.

 

Parent topic:

Device parity protection examples