RAID Drive Setups

Marco Cardazzi

On June 20th In IP Surveillance Video, IP Tech Tips3 Comments

Because of the reality of hard drive failures, security dealers as well as IT personnel must plan and install redundant data recording capability in NVRs and video management PCs.

Backup recording can be performed either manually or automatically. The manual method is the periodic backup of the data on a hard drive(s) onto a different hard drive or medium, such as magnetic tape. This type of backup requires a responsible person to perform this vital function on regular basis, either daily or perhaps weekly. The flaw in this method is that the backup must be performed by a person who might forget, get sick, not come to work on the backup day, etc.

The most common way for data to be backed up automatically is to use one of the RAID (Redundant Array of Independent Disks) configurations that will provide duplication of data without the requirement for a human to get involved or to perform some scheduled function. As the data is recorded it is automatically backed up and/or duplicated by the RAID disk configuration.

There are two commonly used RAID setups. The first is termed RAID 1, which is a simple to understand process. Two disks (or two sets of disks) are configured so that all data that is to be recorded be mirrored onto both disks; everything is immediately double-recorded for storage purposes. The advantage to RAID 1 is the simplicity of the setup and the lower cost with only two disks required. A disadvantage is that accessing data from a RAID 1 configuration will be at the same speed as a single drive, with no improvement of data access quickness.

The other common type of RAID configuration is RAID 5. In this setup a minimum of three disks, or sets of disks are required.

As you can see from the illustration, data blocks are recorded or striped onto different disks, while a separate disk stores a parity block which uses an algorithm to create a combination of two blocks of data that can be reconstructed in the event of a single disk failure. Because the data is spread across the three disks, ordinary access and retrieval of data is faster than RAID 1. With the parity blocks spread across the disk set, theoretically all of the data can be recreated if a disk fails. However, studies have indicated that the reconstruction of data using RAID 5 configurations can be a hit or miss proposition.

For security installation companies who want a sure method of automatic backup it would appear that the RAID 1 setup is the way to go.

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