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Commercial hard drives are not stable storage due to the possibility of errors after a write operation. Techniques such as redundancy and RAID can increase stability, but at the cost of reduced drive size and increased expenses.
Information stored on a computer’s hard drive is recorded as a series of magnetic pulses; it cannot be read, used, or manipulated without the hardware storing it. Physical damage to the drive and other types of system damage, including viruses, can easily compromise the integrity of information stored on a drive by altering or damaging the drive’s storage system. Ensuring stable storage in a computer means building an information storage system guaranteed against immediate failures following a write operation, adding or replacing stored data. Basic commercial hard drives don’t qualify as stable storage by themselves; however, with software and configuration tools, they can meet the needs of stable storage.
To be considered stable storage, following a write procedure – where information is saved to disk – a drive must be able to immediately read back the exact information just written, without errors. This explains why commercial hard drives fail as stable storage: there is always the possibility that a drive will return an error message following any specific write operation. However, there are some techniques to turn commercial hard drives into stable storage devices.
Increasing the stability of commercial hard drives is possible through software management techniques. One software management technique that applies is to force the drive to write to two separate locations on the disk for each write operation, providing redundancy. While one of these places might return an error, the other is statistically unlikely to do the same, resulting in a higher level of stable storage.
Another technique is creating a redundant array of inexpensive disks, or RAID for short. A RAID1 volume is a redundant volume technique known as “mirroring”. It uses two hard drives working in tandem. When a write operation is performed, the same information is written to both drives simultaneously. This provides a real-time backup solution for all data on the drive, making it a more secure form of stable storage.
There are downsides to these techniques. The first is the economy; either way, the actual size of the hard drive is cut in half, as information is constantly being duplicated for backup purposes. The second is the cost; with drives essentially halved, storage expenses can become substantial depending on the amount of data to be saved.
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