Early ATA standard allows 28 bits for data access, in which 8 bits, 4 bits and 16 bits are allocated for Sector, Head and Cylinder respectively, i.e. 2^28 = 137.4 GB storage capacity is available. Besides, ATA-6 standard has allowed 48 bits for data access, in which the support to the general Hard Drives is fully satisfied.
Next we will briefly discuss how to divide a HDD in Linux installation.
Unlike using one primary partition for the active filesystem assigned drive C: within Microsoft Windows scheme, in UNIX-like operating system scheme, a disk device is divided into multiple partitions which allow directories such as /tmp, /usr, /var, or /home to be allocated their own filesystems. Basically we use two partitions in Linux installation: one holding a file system mounted on “/” (the root directory) and the other a swap partition. Nevertheless, here four partitions at least are actually recommended but we won’t discuss this issue in advance because you would realize the importance and advantage of multiple partitions when we talk about filesystems in the later module.
Three major partition types are included when dividing a disk device: primary partition, extended partition and logic partition. One disk device allows four primary partitions at most but extended partition is available if for more than 4 partitions are needed. Please note 4+ partitions are workable only if multiple logic partitions are generated within one (and only one) extended partition because only primary and logic partition can be actually used in operating system while the purpose of extended partition is to contain these multiple logic partitions.