O Google é seu amigo, meu amigo. Estas são descrições muito simples desses dois aspectos do armazenamento de dados.
Volumes
In computer data storage, a volume or logical drive is a single accessible storage area with a single file system, typically (though not necessarily) resident on a single partition of a hard disk.
Blocos
In computing (specifically data transmission and data storage), a block, sometimes called a physical record, is a sequence of bytes or bits, usually containing some whole number of records, having a maximum length, a block size.