Hot Plug / Hot Swap

We always talk about the hard drives that can be hot plugged or hot swapped. Hot-plugging or hot-swapping is great because it allows you to :

• Add hard drives dynamically, so it is possible to change or swap hard drives without turning the system off.
• Replace a defective hard drive without interrupting the normal operation of the computer.

In reality, the hard drive bay and controllers must also be designed to allow for the withdrawal or insertion of hard drives while the system is switched on. This feature is, of course, not available in all systems :

• Although there is usually no physical damage, IDE hard drives do not support this feature and cannot be hot-plugged or hot-swapped.
• This feature is supported by SATA if the controller supports it.
• This feature is supported by SCSI if the controller supports it. However, the bus could be disrupted during the exchange.

Parting Words

RAID systems tend to make users overconfident. However, such excessive confidence in a technology that seems to be very robust and reliable has led to many disasters. Think about it.

Increasing the number of hard drives increases the risk of failure. Moreover, the hard drives used by a RAID array are often the same type and age. They will have a similar  lifespan. The complexity of RAID arrays adds additional risks to the data due to potential problems in the RAID controller or a software bug.

A failed hard drive can also disrupt the functioning of the controller, logically or electrically. This can, in turn, cause the loss of other drives in the array. In the case of a RAID 5 cluster, such a problem will cause the total loss of the cluster.

RAID also does not protect against failures of the operating system (intrinsic or due to a configuration problem or a conflict of components), the destruction of data by a software malfunction, viruses or malicious code. In addition, RAID systems are vulnerable to all conventional physical risks (e.g. fire, flood, theft, lightning and surge external surge within the machine, etc.).

Therefore you should never completely trust a data storage system, even if it is a RAID array. Always perform regular backups and remember that the only reliable way to preserve your data in case of theft or fire, is to store a copy in a separate, distant and secure location.

RAID Optimization

For those who are interested in optimizing their RAID arrays, be sure to check out our RAID Optimization Guide.

Questions & Comments

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