Common RAID Levels

So you’re a home user , your not an engineer , your not an admin but you’re a computer enthusiast , you wouldn’t have a clue what RAID 5 Parity is , but you know what an IDE device is.  As an enthusiast your computer is a massive part of your life. You keep everything on there.  Your photos, your videos, your emails , your porn …. All the important stuff, but as any computer enthusiast, engineer, admin, tech will know …  Hard drives just don’t last.   Iv had hard drives only 3 months old die on me, yea sure I can get it back on warrantee, but who cares? IV LOST ALL MY DATA ! , I couldn’t care less about the price of the hard drive, it’s my gigs and gigs of photos and music iv lost that’s got me tearing my hair out.

So whats the solution?  Buy a cheap Pro-Liant server and host your files off Ultra Wide SCSI Drives in the hope they will last longer?  Err no, too hard..  Buy 1,000 DVD’s and back up your files every week?.  Yea right, im lucky if I do it once a year.

Buy one of those external drives everyone buys now days? And just “Drag and Drop” your files when you need to? .. Meh … Still not great, the point im trying to make here is that you want a solution where your files are backed up instantly without you having to do a damn thing, and better yet, even if your in the middle of watching a movie, it’s a very tense moment, something big is about to happen, the room begins to heat up until “POP CLICK WIRRRR” your hard drive decides to die you, but guess what ??.. Your still watching the movie, you’re completely unaware of what could have been the most disastrous event of your year… And why? Because your PC has automatically switched to your backup hard drive, seamlessly, without even missing a frame on your movie, no reboots, nothing… That’s the beauty of RAID.

The Run Down

RAID stands for Redundant Array of Inexpensive Disks, and it means just that. You can run an array of cheap disks to provide redundancy to your machine.

There are 5 different core levels of RAID, which means 5 different types of RAID setups you can choose from.  There are actually more, closer to 10, but anything other than the first 5 are simply hybrid concoctions of the first 5.  i.e. ,  RAID 10 is a coined phrase that involves a combination of RAID 1 and RAID 0 setups. But for the interest of the home user, im only going to focus on the simple and first few RAID levels.

Within the 5 core levels of RAID there are different methods of data transfer, in other words, there are different ways the data is spread amongst the disks.

Example, Striping.. Striping simply means, if you have 4 disks in a RAID array, then your data is spread among each disk instead of 1 single disk, i.e. “Striped across disks”.

Common Home Use Levels of RAID

RAID-0: This technique has striping but no redundancy of data. It offers the best performance but no fault-tolerance.  This is purely just a performance RAID; it actually reduces your fault tolerance. In a RAID 0 array, if you have 2 disks and 1 fails, the entire array fails.

RAID-1: This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.

This is in my opinion the best solution for the home user. It’s the simplest form of RAID but the most effective.  It simply consists of 2 equal sized disks mirroring each other constantly, If 1 fails, the other will take over until you replace the faulty drive, after which the array will be rebuilt on the fly and your up and running again.

RAID-5: This type includes a rotating parity array, thus addressing the write limitation in RAID-4. Thus, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5 requires at least three and usually five disks for the array. It’s best for multi-user systems in which performance is not critical or which do few write operations.

This basically means you can take a minimum of 3 drives and put them together within a RAID 5 set, and form 1 disk.  Eg , if you took 3 x 300GB Hard disks and created a RAID 5 set,  you would end up with 1 volume approximately 800GB in size . The missing 100GB would be used to store the parity data information that is used to rebuild a disk once one has failed.

Advantages / Disadvantages

RAID 0 Advantages

• Speed , Increased access times due to IO work being load balanced

RAID 0 Disadvantages

• No redundancy
• Risky , If you loose one disk , the array is gone , regardless of the condition of the other disk

RAID 1 Advantages:

• Complete Redundancy
• Increased Read Time

RAID 1 Disadvantages

• Loss of 50% of disk space (From 2 x 200GB disks , you only get 200GB storage)

RAID 5 Advantages

• Complete Parity Redundancy (2 Disks MUST remain in the array other wise the array will fail and your data is gone)
• Maximized space for you hard disks (only around 18% of each disk is lost on parity information)

RAID 5 Disadvantages

• Slower access times
• Difficult to manage sometimes

So How Do I Set It Up ?

Unfortunately there is no easy answer for this, as all main boards will have different RAID controllers, and therefore different methods, although most should be relatively simple.

Setting up a RAID 1 mirroring array is the most common and the easiest. Usually it will mean you’ll have to have 2 cleanly formatted disks of the same size, to which you will create the array on.  Sometimes you’ll designate the primary drive which will handle the majority of work.

The best way to approach a new RAID 1 setup would be to format two disk of the same size , jump into your BIOS or Raid Controller screen and start from there.   If you have any other drives in your system you may want to disconnect them before create the RAID set just incase you get them mixed up and you format the wrong disk.

Your RAID controller will need to be installed in Windows aswell after you have created the array, you will need drivers and most likely some software that came with your mainboard.  This software is generally just there to monitor your RAID set for any failures.

An example would be my setup , to which If I remove the power cable from one of the disks in my RAID array , a small window will pop up instantly in Windows and inform me that one of my disks has failed and it needs to be replaced in order to rebuild my RAID array.

I can carry on and run my machine as normal just on the one disk fine, although if the other disk fails, then the array is gone and Iv lost my data.

Consult your mainboard manual for instructions on how to set up you RAID array, it shouldn’t be hard, and if your mainboard does NOT support RAID, then you can simply buy a PCI RAID adapter that you can RAID you disks on.

Software RAID is crap.  I don’t care what you say, lol.  Its basically like a repetitive  CRON job that copies files from one drive to another.

If you are going to run a SATA RAID array , then you’ll have the ability to hot swap drives, which wont mean much to most users and a reboot isn’t a big drama, but at least you can test it once you get it up and running.  Just simply remove the SATA cable from the drive when in windows and wait to see if you get a message informing you, your RAID array has been compromised.

So you’ve got no excuse , with hard drive prices so cheap now days, you’d be an idiot not to set up some sort of cheap RAID array , get out there and do it , and never again fear that your 100GB pr0n collection might just disappear one day.