Ok i need to understand how raid 5 can tolerate loss of one drive. I assume that we have a 4 hd(250 gb) raid 5 .we lose the storage capacity of one drive or the storage capacity is 750 *0.75= 562.5. If the first is true i really dont understand how. That was my thoughts here is the answer: http://www.scottklarr.com/topic/23/how-raid-5-really-works/ Just in case some noob like me thinks that somenthing is missing
Gee almost 2 months and no answer? Here it is... Raid 0 - The 0 indicates how much data you can recover when a drive dies. Raid 0 simply bonds multiple disks into one big one, so you have all storage space of all devices. But no failure tolerance. Raid 1 - you have a mirror of a drive. 2 physical devices, constant mirror. One drive dies, you can break the mirror and use it solo, or you can remove the bad drive and rebuild the mirror. Raid 5 - you have at least 3 drives. Depending on how you are doing the raid you may be able to have one as a hot spare. You get 2/3 of your storage space. Data is written in a way that for each pair of bits, each one is on a different physical device and there is a parity bit on yet a different physical device. Depending on which physical device dies, each triplet will loose one of them - bit 1, bit 2, or parity - but with the other 2 existing, the 3rd can be quickly calculated and replaced onto the replacement drive.
