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 type | Drive device name |
|---|---|
| IDE hard drives | ad in 4.0-RELEASE, wd before 4.0-RELEASE. |
| IDE CDROM drives | acd from 3.1-RELEASE, wcd before 4.0-RELEASE. |
| SCSI hard drives | da from 3.0-RELEASE, sd before 3.0-RELEASE. |
| SCSI CDROM drives | cd |
| Assorted non-standard CDROM drives | mcd for Mitsumi CD-ROM, scd for Sony CD-ROM, matcd for Matsushita/Panasonic CD-ROM |
| Floppy drives | fd |
| SCSI tape drives | sa from 3.0-RELEASE, st before 3.0-RELEASE. |
| IDE tape drives | ast from 4.0-RELEASE, wst before 4.0-RELEASE. |
| Flash drives | fla for DiskOnChip Flash device from 3.3-RELEASE. |
| RAID drives | myxd 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. |
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>.