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|
|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>.