Denis Joseph Nexum Hardware.

Adaptec Scsi

Raid, What is it and why do you care?

RAID is an acronym for Redundant Array of intelligent disk. Sometimes, the acronym is cited as Redundant Array of Intelligent Devices or Redundant Array of Inexpensive Disks. In any case, there is a group of hard discs to optimize your storage according to your individual needs. The optimization is done with the software (Software RAID) or hardware (hardware RAID). Hard drives configured in a configuration Are called a RAID array. There are many types of RAID some of them you can see reference are RAID 0, RAID 1, RAID 5, RAID 6, JBOD, and then there are tables combination that sometimes are referred to a two-digit number and sometimes as a number + another number. Ie RAID 0 +1 or RAID 10, RAID 1 RAID 5 or 15. Because different sources to identify these configurations differently I will not attempt to identify all possible configurations and all possible acronyms for them. I will however try to explain what are the most common types of RAID, and how they can affect your small business.

RAID 1 provides redundancy disk drive. Two identical hard drives installed, one is loaded with the operating system and all your programs and data, other copies of the first hard times. This is called a mirror and if one disk fails, you can set the other player to assume without loss of data and no downtime. The disc can be replaced later, or even when running on certain configurations (This would be the most expensive).

Mirroring is strongly recommended for operations of small business, you can not risk losing your data or close your network while you try to recover your data. The disadvantage of mirroring is that the copy process slows the system a bit. If you use a mirror RAID software, the slowdown will be visible, but not unreasonable. hardware mirroring is almost undetectable.

RAID 0 delivers high performance, commonly called striping. Two (or more) identical drives are installed and the RAID controller configures both as a disk about twice the size. When the system reads or writes on the new disk only, it actually reads or writes data tapes on two discs same time. This reduces the time required for accessing or storing data. The problem with interlacing is that if a disk fails, all data is lost. (Bummer!)

A common compromise used RAID 10, which stripes two sets of two drives for speed, and mirrors, then a broken record to another. The end result is faster than an ordinary mirror, and slower than a broken record regularly. If one disk fails, the mirror band continues to operate. The disadvantage is that you need 4 or more drives, which drives costs upwards.

RAID 5 was designed to solve all problems. RAID 5 on three or more disks in the process, he wrote a strip additional recovery. If a drive fails, other players can reconstruct the data from band recovery information. Yet Once that is often offered in a "hot swap" arrangement so that the reader of death can be replaced and rebuilt without even rebooting the machine. Until recently, RAID 5 was only available in high end SCSI configurations, is not common in small offices. The only drawback RAID 5 is that you lose about 1 / 3 of total capacity disk recovery tape. (A small price to pay!)

RAID 6 is a new configuration touted by Intel and others as the next generation. At this point, I'll let the benefits of RAID 6 for you to decide for yourself if you're interested. To learn more about target = "_blank"> here.

JBOD is "Just a Bunch Of Disks". Basically, you have a RAID controller and you use it only to increase the number of readers you have. There is no real function in JBOD RAID in the traditional sense.

This makes RAID a point of interest right now is the development of the SATA II standard and the introduction of SATA RAID controllers built on inexpensive motherboards. In the past, it was not uncommon for RAID 0, 1, 0 +1, RAID 5, but was only SCSI. Today you can buy a motherboard for $ 200 or less with SATA II RAID 0, 1 and 5 (and all combinations) built on. In addition, you can buy SATA II controllers from companies like Adaptec that allows you to run any SATA RAID configuration you want on just about any How modern motherboard you want.

The real kicker here is that SATA drives are inexpensive. In the past include a RAID disk SCSI drive that cost in the neighborhood of $ 500 each, which gives you about 146. So take a hard drive RAID 5 five solutions as an example: Five drives of 146 GB at $ 500 = $ 2500 would be around 487 GB of space efficiency. In addition, a SCSI RAID 5 controller card is required, it is generally run $ 350 to $ 700 more. Server grade motherboards come with built in SCSI RAID 5 controllers, but the cost was easily $ 300 higher than a motherboard without the controller. So here is the final cost between $ 2,800 and $ 3,200, or a minimum of $ 5.75 per GB

Now let's look at the new SATA II RAID 5: You can buy a motherboard for under $ 150 with onboard RAID 5, or a SATA II RAID Controller for about $ 5 200 to $ 250. You can buy five 250 GB SATA II for something like $ 300. This would give about 833 of the space. The final cost is then between $ 650 and $ 750 or $ 0.78 per GB down.

Now let's take a look at the cost of mirroring. If you have a Windows 2000 or newer you can run a software mirror that is built into the operating system, as I said there will be a detectable slowdown in the system. Alternatively, you can run a mirror of your server hardware, or even on a single desktop. The cost for both hard drives and a controller card would in the neighborhood of $ 300 to $ 350. SATA II RAID 1420SA Adaptec cards like without the RAID 5 function, are about $ 150, and 500 GB drives are about $ 100 each.

Consider what would happen tomorrow if you were at work, and your hard drive has failed. If you've read this page then you probably have a copy of backup, but how long will you be while you replaced the disk, the software reinstalled and restored data from backup? You DO have a backup, right?

Would you pay $ 300 to make sure you never lose your data without having Turn off the power during a busy working day because of an outage?

I would (already).

Just FYI. Here are some website with more information on RAID. Remember, a few details like the acronyms do not agree with an author to another, but the concept and execution are the same.

href = "http://www.ecs.umass.edu/ece/koren/architecture/Raid/raidhome.html" target = "_blank"> University of Massachusetts

target = "_blank"> Adaptec

About the Author

Steve Weigle is the owner of Village Geek Computers, an IT center with multiple locations. Steve has provided IT services to Central Indiana since 1996.

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