10.3. Disk Naming

Physical drives come in two main flavors, IDE, or SCSI; but there are also drives backed by RAID controllers, flash memory, and so forth. Since these behave quite differently, they have their own drivers and devices.

Table 10-1. Physical Disk Naming Conventions

Drive typeDrive device name
IDE hard drivesad in 4.0-RELEASE, wd before 4.0-RELEASE.
IDE CDROM drivesacd from 3.1-RELEASE, wcd before 4.0-RELEASE.
SCSI hard drivesda from 3.0-RELEASE, sd before 3.0-RELEASE.
SCSI CDROM drivescd
Assorted non-standard CDROM drivesmcd for Mitsumi CD-ROM, scd for Sony CD-ROM, matcd for Matsushita/Panasonic CD-ROM
Floppy drivesfd
SCSI tape drivessa from 3.0-RELEASE, st before 3.0-RELEASE.
IDE tape drivesast from 4.0-RELEASE, wst before 4.0-RELEASE.
Flash drivesfla for DiskOnChip Flash device from 3.3-RELEASE.
RAID drivesmyxd for Mylex, and amrd for AMI MegaRAID, idad for Compaq Smart RAID. from 4.0-RELEASE. id between 3.2-RELEASE and 4.0-RELEASE.

10.3.1. Slices and Partitions

Physical disks usually contain slices, unless they are "dangerously dedicated". Slice numbers follow the device name, prefixed with an s: "da0s1".

Slices, "dangerously dedicated" physical drives, and other drives contain partitions, which represented as letters from a to h. b is reserved for swap partitions, and c is an unused partition the size of the entire slice or drive. This is explained in Section 10.5>.