Please remember, all drives should have exactly the same capacity if you want to use it in a raid array. If your drives have different capacities, the raid array will always use the size of the smallest drive.
RAID 0 #
RAID 0 – stripe set or striped volume – it splits data across between two or more drives. RAID 0 doesn’t provide any kind of redundancy, fault tolerance or information parity. If one of the drives will fail, you will lose all of your data inside.
Performance of RAID 0 is rising n times where n is number of drives inside raid array.
RAID 1 #
RAID 1 – mirroring – data are copied 1:1 on all drives inside raid 1 array. There’s no stripping, spanning or parity across multiple drives. RAID 1 will be operational as long, as at least one drive is working. This configuration is very useful for reading performance.
Read requests are served by any drive in the array, it’s depending on the I/O load. However read performance is equal to the sum of drives, that write performance is at the level of one single drive.
RAID 5 #
You need at least 3 drives for using the RAID-5 layout. The capacity of the entire RAID-5 array is N-1, so it means if you have three 1TB drives, the capacity of the entire RAID array is 2TB.
RAID-5 offers better read performance than RAID-1, however, the write performance is a bit lower. If one of the drives fail and will be replaced with a new one, the RAID array will rebuild itself, however, the performance of reading/writing will be lowered during the recovery process.
If your RAID-5 will lose more than one drive, your data will be not recoverable.
RAID 6 #
RAID 6 is extending RAID 5 by adding an additional parity block. It’s much safer than RAID-5 – if two drives fail, your data are still readable.
RAID 10 #
It’s like a RAID-0 array with elements of the RAID-1 array. You need at least four drives to configure RAID-10. The capacity of the RAID-10 array is N / 2, which means, if you have four 2TB drives (total capacity of 8TB), your usable capacity is 4TB. RAID 10 joins the performance of RAID-1 and the safety of RAID-1.