The translation is only a problem for IDE disks. SCSI disks use a sequential sector number (i.e., the controller translates a sequential sector number to a head, cylinder, and sector triplet), and a completely different method for the CPU to talk with the controller, so they are insulated from the problem. Note, however, that the computer might not know the real geometry of an SCSI disk either.
Since Linux often will not know the real geometry of a disk, its filesystems don't even try to keep files within a single cylinder. Instead, it tries to assign sequentially numbered sectors to files, which almost always gives similar performance. The issue is further complicated by on-controller caches, and automatic prefetches done by the controller.
Each hard disk is represented by a separate device file. There can (usually) be only two or four IDE hard disks. These are known as /dev/hda , /dev/hdb , /dev/hdc , and /dev/hdd , respectively. SCSI hard disks are known as /dev/sda , /dev/sdb , and so on. Similar naming conventions exist for other hard disk types; see Chapter 4 for more information. Note that the device files for the hard disks give access to the entire disk, with no regard to partitions (which will be discussed below), and it's easy to mess up the partitions or the data in them if you aren't careful. The disks' device files are usually used only to get access to the master boot record (which will also be discussed below).
Prev
Home
Next
Two kinds of devices
Up
Storage Area Networks - Draft
