117. Installing RAID

By Andrew D. Wright

RAID is a way of overcoming the two major physical limitations of hard drives - that they are the slowest part of the computer and they tend to break down.

To recap, with RAID 0 you can make two hard drives act as one single fast hard drive, perfect for gamers or people working with very large files like graphics design or video editing applications.

With RAID 1 you can make two hard drives that are mirror copies of each other. In the event of a hard drive crash, there is no data lost and no downtime. Accountants or other professionals who need full-time data access and data integrity could use RAID 1 to act as a backup system that updates in real time.

It's best to start with two new hard drives, both the same size and ideally the same make as well.

There are two basic types of RAID setup: hardware RAID and software RAID. Hardware RAID requires a RAID controller built into the motherboard or a specialized controller card. Budget controller cards use software RAID, as do the Professional versions of Windows XP and 2000.

Hardware RAID is the best way to go. It's faster, presenting the two new hard drives to the operating system as one drive, making control of the drives by the operating system more efficient.

If your motherboard supports hardware RAID there will be an option in the computer's BIOS to enable the RAID controller. The BIOS is the first thing you see when your computer starts up. Consult your computer documentation for how to access the BIOS and setup the RAID controller.

Many new motherboards support hardware RAID control for new faster SATA hard drives. SATA hard drives use a connection cable about as wide as a piece of chalk while older IDE hard drives use a ribbon cable about as wide as a credit card.

When setting up RAID using IDE hard drives, each hard drive should be alone as the master on its own cable and controller. Putting the two drives together on one controller will slow things down as only one drive can be written to at a time.

Installing the hard drives is straightforward. With the computer turned off, connect the data cable and the power cable to the each hard drive and connect the other end of the data cable to the controller.

A motherboard RAID controller, once enabled in the BIOS, will detect the hard drives on startup and offer a setup menu. Setting up the drives this way is very easy for anyone to follow - the usual format is do nothing and the drives will be detected as two separate drives, select RAID 0 to stripe the data between the two disks for greater speed or lastly, select RAID 1 and mirror the data between the two drives for greater data safety.

If using a budget RAID controller card, the card will need to be physically installed then detected in Windows. The hard drives connected through it can be setup using the controller card software, installed from the CD that came with the card. The Help documentation included with the RAID controller card will explain setup and use of the software.

To make the drives usable by Windows they need to be partitioned and formatted. Right click on My Computer and select Manage. Where it says Computer Management (Local), look under Storage for Disk Management. Select Action then Rescan Disks to detect the new hard drives

To put a partition on a new drive, right click on the hard drive in the Disk Management window and select New Partition. Select Primary Partition and the maximum size allowed for the partition. Formatting the drive can use the default values and the NTFS file system.

Without a RAID controller users of the Professional versions of Windows XP and Windows 2000 can setup RAID 0 using Windows Disk Management.

Right clicking on the new drive will allow the option to setup the drive as dynamic or basic. Set each of the two drives as dynamic.

Right click on the unallocated space on one of the new drives and click New Volume. Under Select Volume Type pick Striped then add the second hard drive for the RAID 0 array. Use the maximum space for the new volume.

Here's my results for RAID using two new 500 GB SATA hard drives. The motherboard controller is using hardware RAID, the budget PCI card RAID controller and Windows XP Professional are using software RAID. As with all measurements of active systems with varying components, these figures are meant only as a guide. Your results may vary.

	Single drive Motherboard controller [Reference]	RAID 1 [Mirror] Motherboard controller	RAID 0 [Stripe] Motherboard controller	RAID 0 [Stripe] Budget PCI card controller	RAID 0 [Stripe] Windows XP Pro Software RAID
Buffered Read	103 MB/s	103 MB/s	138 MB/s	98 MB/s	88 MB/s
Sequential Read	82 MB/s	82 MB/s	145 MB/s	103 MB/s	99 MB/s
Random Read	9 MB/s	9 MB/s	8 MB/s	8 MB/s	5 MB/s
Buffered Write	86 MB/s	60 MB/s	102 MB/s	77 MB/s	44 MB/s
Sequential Write	77 MB/s	69 MB/s	119 MB/s	87 MB/s	87 MB/s
Average Access Time	7 MS	7 MS	8 MS	7 MS	12 MS

As you can see, there is a major speed advantage to using hardware RAID 0 (striped data) over the reference drive and over software RAID using either Windows or a budget controller card.

Mirroring data with hardware RAID 1 is slightly slower in writing data than the reference drive speed but reading speeds are identical. Most people would see no difference in performance.

 

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Originally published 23 September 2007

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