Simple RAID Explanation covering JBOD and RAID Levels 0, 1, 5 and 6
What’s the difference between RAID 0 and 1? Is RAID 5 the best? If you find yourself asking these questions here’s a quick summary of the standard RAID levels. For the sake of simplicity, I’m only going to cover JBOD, RAID 0, RAID 1, RAID 5 and RAID 6.
JBOD (Just a Bunch of Disks) or Spanned Array
JBOD isn’t an official RAID setup, but most RAID setups offer it as an option. A JBOD array basically takes a bunch of disks and turns them into one big partition. JBOD offers no redundancy and with some RAID setups, the failure of one disk in the array will cause the whole JBOD array to fail. Unlike RAID 0, a JBOD array reads and writes at the same speed as a normal disk.
RAID 0 or Striped RAID
The first level of RAID is RAID 0, commonly referred to as striped RAID. This level of RAID is only for users looking for speed. RAID 0 requires at least two drives. RAID 0 is very dangerous for users looking for reliability. If one disk in the RAID array dies the whole array is trashed. Generally the more disks in the array the faster read and write times will be, but the greater the chance of the array failing. The size of a RAID 0 array is the size of all the drives in the array combined.
RAID 1 or Mirrored RAID
The second level is RAID 1, also know as mirrored RAID. This level of RAID will increase reliability, but requires two drives of the same size. RAID 1 makes an exact copy of a hard drive therefore using 50% of the total storage for redundancy. For example, if a user has two 500GB hard drives making their array 1TB they will have 500GB of actual storage. In most RAID setups, RAID 1 will increase the the read speed but will slightly decrease the write speed.
RAID 5
RAID 5 is my favorite level of RAID for secure storage of files. RAID 5 requires at least 3 drives to operate and will continue to work even in the event of a drive failure. RAID 5 is more efficient than RAID 1 when it comes to data storage. RAID 5 uses just one disk in the array for redundancy. So the more drives in the array the more efficient the array becomes. For example, if a user had three 500 GB hard drives totaling 1.5 TB and they were using RAID 5 they would have about 1 TB of actual storage. This makes RAID 5 much more efficient than RAID 1. RAID five has considerably slower write speeds than RAID 1 or a standalone drive, but read speeds are often increased.
RAID 6
RAID 6 is almost the same as RAID 5 but it can sustain 2 drives losses instead of 1. RAID 6 requires at least 4 drives to operate and will continue to work even if two drives are missing. RAID 6 is best used for mission critical applications. The greater the total number of drives the more efficient the array becomes. Storage can be calculated by adding up the total number of drives in the array and subtracting two drives. For example, if there are four 500GB drives in the array there would be 1TB of available storage.
[...] first step is to decide what type of RAID will be needed. This can be done by looking at my article describing the different types of RAID that are available in the modified Windows XP Pro. Once the type of RAID is decided upon, [...]
Pingback by Software RAID 0, 1, 5 or JBOD Using Windows XP Pro SP3; Network Accesable from Linux, Mac OS X and Windows | JonFleck.com — March 3, 2009 @ 4:21 am
Two comments:
1) When data is written to disks in stripes, it is called a striped array, not a stripped array. Reference IBM or Wikipedia for spelling of “stripe”.
2) The overhead for RAID 5 is not “roughly” 33%. It is 33.3%, 25%, 20%, 16.7%, 14.3%, 12.5%, etc.
Comment by Joe — April 24, 2009 @ 5:15 am
[...] first step is to decide on the type of RAID. Go to my article on simple RAID level explanations to find out the differences between the different levels or RAID. Once the desired RAID level is [...]
Pingback by Optimiz3.com » Installing Fedora 11 and Setting up a RAID 0, 1, 5, 6 or 10 array — July 24, 2009 @ 12:02 am
[...] Click Next at the first step of the New Volume Wizard. The second step of the wizard is to select the volume type. If you’re not sure what type of volume you want, check out Simple RAID explanation covering RAID levels 0, 1, 5 and JBOD. [...]
Pingback by Optimiz3.com » Software RAID 0, 1, 5 or JBOD Using Windows XP Pro SP3 — July 25, 2009 @ 6:42 pm
Yous say that raid 5 uses 1 disk for redundancy but actually raid 5 uses every single disk on the array for that use, in fact this is called parity handling. This his set to optimize the exchanges on all disks and also avoid an overload of one disk precisely. also if you have 5 disks on raid5 all of your disks are used for parity handling. If more than one crash, your raid is dead … see more information here : http://en.wikipedia.org/wiki/Raid_5#RAID_5
Comment by Nicolas Blanc — January 19, 2010 @ 7:44 pm
My Mobo has 2 ide ports and 2 sata ports. I am using the IDE ports for my CD/DVD drive and my primary HD. I am wanting to use the sata ports for 2 seperate sata HD’s. One that has my music on and one that has my pictures on. The mobo supports Raid 0 and Raid 1. What would I need it set to??
Comment by Paul @ free xbox live — February 17, 2010 @ 1:48 pm
I use RAID level 1 with 2 matching 500 GB Western Digital Raptor harddrives in case a harddrive dies I still have the Windows 7 operating system and all the files.
harddrives are cheap compared to what they used to cost in 1990.
Comment by John — February 26, 2010 @ 1:22 pm
Thank you for providing clear, simple explanations and some commentary on the prospects for each method. Very helpful for someone like me, who has finally decided to “go RAID” and get some depth of security for “all that stuff” we seem to collect.
Comment by George Baumann — July 29, 2010 @ 1:58 am
When I get to the new volume wizard my only choice is the simple option. I want to create raid 1.
Thanks for your help
Comment by Darby Drake — August 18, 2010 @ 2:08 pm