What is block I/O?
Block I/O is ultimately what is done to a disk drive. Disks today in open systems store data in fixed blocks (usually 512 bytes) in a linear address space. Doing block I/O means that the application or file system is sending blocks to the disk drive to be written or asking for blocks using a logical block address (LBA). File systems turn file requests into block I/O. Applications (including databases) can do file I/O or they can bypass the filesystem and do block I/O (this is usually called raw I/O). Obviously it's easier to do file I/O, and you can do file sharing much easier that way. Doing block I/O may have performance advantages (in control of the buffering/caching and not having the file system overhead).
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