Please help me to understand about sequential io vs random io? what are the difference?
which will (sequential io vs random io) better performance? In Storage why random io is too high comparing to sequential io?
random and sequential IO are nothing but access pattern of the data which is also dependent on how the application wants the data access.
"Random" means you can get any part of the file in any order. So for example, you can read the middle part before the start.
"Sequential" means you must first read the first part of the file, before reading second, then third etc.. figure below explains .
Accessing/writing data sequentially is much faster than accessing/writing it randomly because of the way in which the disk hardware works. The seek operation, which occurs when the disk head positions itself at the right disk cylinder to access data requested, takes more time than any other part of the I/O process. Because reading randomly involves a higher number of seek operations than does sequential reading, random reads deliver a lower rate of throughput. The same is true for random writing.
In older times, when playing a record, the needle/head follows one track around the surface of the disk. This is sequential read. The difference between sequential read and random read is a random read is similar to if you pick up the head and try to find the next track and let it play. Doing so causes music to stop playing while there is a "random" seek.
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