Differences between stripped or concatenated RAID mode

With striped, all the even numbered blocks go on one drive, the odd numbered on the other drive. The drives have to be the same size.

With concatenated, the first drive has the lower numbered blocks, the second the higher numbered blocks. The drives can be different sizes.

With striped, all disk operations will go at twice the transfer rate if they involve more than one block. With concatenated, you only get more performance if you are simultaneously using files that happen to be on different drives.

The same principals apply if the RAID has more than two drives. With either striped or concatenated, if one drives fails you lose all the data. (With concatenated you may be able to recover some data from the remaining drive by using special recovery software.)

Hi Steve@Mac;

If you have three drive in the striped RAID array then the data is divided out three ways. Think of it a bit like dealing cards. The dealer gives everyone at the table a card and then repeats that going around again until the hand is dealt. Striped RAID is a bit similar in that the controller sends data to each disk in the array in turn until all the data has been sent out.

Allan

Hi Steve@Mac;

No. Going back to my card analogy, if someone else sits down in the game, you have to deal the hand once more. Since the data is divided up n ways, adding anothter drive means it must be divided up n+1 ways. Hence the data will have to be backed up and restored after the drive is added to the array.

I going to flog this card analogy for all it is worth!

Allan