Introduction to RAID arrays, basic concepts, sequential vs. random I/O, mechanical vs. SSD drives

A basic introduction on the underlying concepts of RAID arrays.
Here we look at why do we actually need RAID compared to single disks. Namely, to improve the I/O capabilities of storage disks, RAID arrays are often used in enthusiast personal computers, and in industrial/production environments they are considered long ago as a must from the onset.
In this video we discuss the main limitations of a traditional mechanical disk and compare it to a more modern solid state disk. The sequential and random data access patterns on the disk are being explained as well. Also, the issue of the single point of failure is discussed. Next, we turn our attention towards the very basic idea of RAID, which is practically nothing else but to use multiple independent disks attached to the same data bus, and split the load among the different disks, and build an array out of them.
Depending on the chosen RAID levels, the hardware RAID controller (or the software RAID, depending on implementation) uses different RAID logic to do this load sharing. This way one can reach faster sequential or random I/O speeds, or improve the data security. In small environments the RAID 0, RAID1 and RAID5 are the most frequently used standard RAID levels.