FEATURES of the stripes are not compromised. It requires a minimum of four disks to establish.
IMPLEMENTING RAID RAID can be implemented using specialised hardware, software, or the RAID functionality built into most modern operating systems. Disks can be housed either inside the computer, or within external disk enclosures. Hardware RAID A hardware RAID controller is simply an expansion card that is inserted into a slot on the computer’s motherboard. These cards are specially designed to perform parity calculations, come equipped with high-speed connectors for multiple hard disks, and offer many other features. RAID controller cards are available in port configurations that support either internal hard disks, external hard disk enclosures, or a combination of both. Software RAID Another option involves connecting the hard disks to the Serial-ATA ports found on modern computer motherboards, or optionally, installing a Serial-ATA card into an available motherboard expansion slot and plugging the hard disks into the ports on this card. As with dedicated RAID controllers, these Serial-ATA expansion cards are available in configurations that support internal hard disks, external hard disks, or a combination of both. Unlike dedicated RAID controllers, SerialATA cards and the ports found on most motherboards do not have the ability to create RAID sets themselves. Instead, they are reliant on the server’s operating system or a third-party software solution to arrange the connected hard disks into the desired RAID arrangement.
External Disk Enclosures External disk enclosures are selfcontained units that simply contain a power supply and space for hard disks. Some units also contain a RAID controller card, allowing the disks installed in the enclosure to appear outwardly as a single disk, negating the need for any additional configuration to be performed on the computer. External disk enclosures can be hooked up via a USB port, or via a number of other connection types such as FireWire, SCSI or Serial-ATA. While USB and FireWire are suitable interfaces for external backup solutions (whether they be a RAID or a single disk product), Serial-ATA is the most suitable interface with which to connect a RAID solution hosting live practice data.
REBUILDING AN ARRAY Redundancy-enabled RAID solutions provide the ability for the system to continue functioning, even when one of the disks in the array has failed. When this occurs however, performance is adversely affected and the array is described as operating in a “degraded” state. If a failed disk is replaced with a functioning disk, the hardware or software controller will proceed to rebuild the RAID set, restoring full redundancy capabilities to the system. This restoration process can be timeconsuming, and while the array will function properly during this time, the performance will be diminished. Although replacing an internally installed hard disk is relatively straightforward for an IT savvy person, external disk enclosures that feature hard disks mounted in trays or drawers simplify
the task to the point where even the most technologically shy practice staff member could be trained to perform the process unassisted, or guided through the steps involved over the phone by an IT support professional. Excess disks in certain RAID arrangements can be designated as “hot spares”. When such a disk is available, the RAID controller can automatically start rebuilding the system, minimizing the amount of time that the array is vulnerable.
DO I STILL NEED TO BACKUP? While the use of an appropriate RAID scheme can reduce the risk of hardware related data loss, it certainly does not completely mitigate it. Further, RAID does not protect against user error (e.g. the accidental deletion of files), nor from corruption caused by application software or the operating system. As such, the existing backup arrangements practices have in place still need to be followed.
CONCLUSIONS RAID has long been used by large organisations to maintain high levels of server availability. Recent improvements in storage technology and the falling cost of hard disks and associated hardware now make RAID easily accessible to small businesses, and ideal for deployment in medical practices. Practices that do not yet enjoy the data protection that RAID delivers are advised to discuss the feasibility of implementing an appropriate RAID system with their IT support professional. René Yim has a background in data analysis and is presently involved in managing risk for a financial institution.
Below - Graphical representations of three popular RAID arrangements. RAID 0 stripes data over two or more drives, improving performance but not redundancy. RAID 1 mirrors data on two or more drives for the purpose of increasing redundancy. RAID 5 stripes data over three or more drives, distributing parity (redundant) data across all drives in the RAID set. [Images sourced from Wikipedia]
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