Why SMR drives are generally not optimal for RAID configurations?

In a traditional HDD, data is written to tracks that are laid down in parallel on the disk platter. Each track is separated from its neighbors by a small gap. When data is written to a track, the read/write head moves across the track, and write the data to the magnetic surface.

In an SMR drive, the tracks are overlapped slightly. This means that when data is written to a track, it can overwrite data that was previously written to an adjacent track. To avoid this, the drive must first read the data that will be overwritten and store it in a buffer. Then, the drive can write the new data to the track.

Advantage:

1. Increase in disk surface density

2. Increased write latency

3. Reduce cost per gigabyte

Shortcoming:

1. Increase processing requirements

2. Improve energy efficiency

3. Not suitable for low-latency applications

SMR drives are generally not optimal for RAID configurations:

1. The overlapping track design of SMR drives, while beneficial for increasing storage capacity, can lead to performance bottlenecks. This is especially evident in write-intensive operations where writing to one track may necessitate the rewriting of adjacent tracks, thus slowing down the process.

2. RAID arrays require consistent and fast read/write access to all drives, but the sequential write necessity of SMR drives can introduce delays. These delays can extend RAID rebuild times and elevate the risk of operational errors and data integrity complications, making SMR drives less suitable for RAID applications.