UK INFOWEB

TG Systems

RAID' (Redundant Array of Inexpensive Disks) is a method of protecting your system, programs and, most importantly, data.  In simple terms the main system disk is physically duplicated and everything written to disk is written onto both disks, providing a dynamic backup that's always up to date.  If one disk fails a warning is given and it can be replaced without any loss of data or system information.  You can even keep your system running until you get a replacement drive, but of course you won't have the protection of RAID until you do!

Implementation. To convert an existing system disk to RAID, we use the latest high speed 'SATA' drives.  Your existing drive is copied onto the two new drives.  The drives are then installed in the PC, together with the RAID hardware.  Finally, the RAID software is installed and activated.  This will also confirm that the two drives have identical contents.  The process takes 2 to 3 hours. 

Technical Information

RAID  came out of efforts to combine several inexpensive drives to equal or exceed the performance of a larger and more expensive disk drive.  Now, the greatest benefit for the business user is derived from the redundancy aspect of RAID 1 (see below).  There are lots of different types of RAID that involve the storing of error checking and parity data.  Briefly described here are the RAID uses that the vast majority of us could benefit from, RAID 0 and RAID 1. 

RAID 0: Striped Disk Array. Strictly speaking 'AID' as there is no redundancy.  Data is written in stripes, alternately to two drives - this increases throughput as writing to the two disks is performed simultaneously.  However, as there is no redundancy (duplication), there is no data protection - a failure loss of either disk (in a 2-disk array) results in the total loss of data!

RAID 1: Mirrored Disk Array A mirrored disk array is composed of a set of two physical hard drives, each of which contains a full copy of all data sent to the logical drive that represents the array. This has a couple of advantages; first of all, any data stored on a RAID 1 array is completely and automatically backed up, and in the event of the failure of one drive, the other can be substituted without a hitch. Secondly, data can be read from both drives simultaneously, increasing the speed of data retrieval.

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08 Feb 2007