RAID
How Important Is Your Data?

How Important is RAID(Redundant Array of Independent Drives)? RAID is generally reserved for computers on your network providing file and or application responsibilities. In plain English, how important is it that you lose no data? In an office situation, how difficult would it be for you to re-key all data lost since the last backup? Consider a Dentist who is storing patients digital x-rays. A hard drive failure without RAID means patients would have to be recalled and x-rays be redone, which may not be possible! Drives are so affordable that a four drive 250GB array only cost around $500.00. Using RAID level 5 or 0+1 gives you great storage capacity, redundancy or fault tolerance, and increased Read/Write speeds.

RAID is a combination of physical drives combined to work as one logical drive in various predefined levels. While the operating system sees only the logical unit (Array) the Raid controller works at the physical drive level. RAID levels are set by either software or hardware controllers. Windows Server 2000 and 2003 have software RAID controller capabilities as part of the operating system. Windows desktop operating systems like Windows 2000 Professional, Windows XP Professional, or Vista do not. Hardware RAID controllers are generally better because they offer additional RAID levels without compromising CPU availabilty or reduce available RAM Memory from the Operating system.

Most motherboard manufacturers have a model that includes an Onboard Hardware Raid controller. Intel's, Matrix Storage Technology, lets you start out with a single drive, and when you decide to implement RAID, you simply add the drive(s) and setup the level of RAID protection you require. ExtremeTech compared Adaptec, LSI Logic, and Promise RAID controllers against Intel's ICH7R Onboard controller. The conclusion is that Intel's onboard raid controller handily beat out the other four in nearly every test. This is even more important when you consider Intel's 975x motherboard cost less than some of the Raid controllers it beat during the test. For facts and figures, here is the article at ExtremeTech.com

To find out if your Motherboard has RAID capability, you need your motherboard’s manufacture and model number. To find your motherboard model number in Windows XP click: Start> Programs> Accessories> System Tools> System Info>. Find the two line items System Manufacturer (Motherboard) and System Model (Motherboard Model #).

RAID LEVELS EXPLAINED - Which one fits your needs? I am going to limit our discussion of RAID Levels to 0,1,5,0+1. There are other standard RAID levels such as 10 and 50 as well as Custom or Proprietary Levels created by specific vendors.

Level 0 - Striping - Level 0 requires a minimum of two physical drives. A single file is broken into blocks and each block is written to multiple drives. This will double the Read and Write speeds to the drives but offers no fault tolerance. Since all physical drives are seen as one logical drive, if any physical drive fails the entire logical drive fails. Example: Install two 100GB physical drives and create one logical 200GB array. See acnc.com.

Level 1 - Mirroring - Level 1 requires a minimum of two physical drives. A single file is written to two physical disks at one time. If either physical disk fails the other disk has the exact data. This increases the Read performance because the operating system will Read from both drives at the same time while the Write speed is the same as a single disk. Example: Install two 100GB drives and create one logical 100GB array. See acnc.com

Level 5 - Striping + Parity - Level 5 requires at least 3 physical hard drives. A single file is broken into blocks and each block is written to multiple drives plus a parity block. This parity block allows the logical drive to withstand a single physical drive failure while maintaining logical drive integrity. This level offers the highest Read data rate while offering only medium Write data rate. Example: Install four 100GB drives and create one logical 300GB array. See acnc.com

Level 0+1 - Striping + Mirroring - Level 0+1 requires a minimum of four physical hard drives. You setup two sets of striped drives that mirror each other. This offers the highest Read and Write data transaction rates. With four physical drives this level of Raid gives you four times the Read data rate and twice the Write data rate of a single drive. Example: Install four 100GB physical drives and create one logical 200GB array. See acnc.com

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