HP UX Operating Systems manual 553

mediainit(1)	mediainit(1)
pathname	pathname is the path name to the character (raw) device special ®le associated with
	the device unit or volume that is to be initialized. mediainit aborts if you lack
	either read or write permission to the device special ®le, or if the device is currently
	open for any other process. This prevents accidental initialization of the root device or
	any mounted volume. mediainit locks the unit or volume being initialized so that
	no other processes can access it.
	Except for SCSI devices, pathname must be a device special ®le whose minor number
	of the device being initialized has the diagnostic bit set. For device special ®les with
	the diagnostic bit set, the section number is meaningless. The entire device is
	accessed.

When a given unit contains multiple volumes as de®ned by the drive controller, any available unit or volume associated with that controller can be initialized, independent of other units and volumes that share the same controller. Thus, you can initialize one unit or volume to any format or interleave factor without affecting formats or data on companion units or volumes. However, be aware that the entire unit or volume (as de®ned by the drive controller) is initialized without considering the possibility that it may be subdivided into smaller structures by the the operating software. When such structures exist, unexpected loss of data is possible.

mediainit dominates controller resources and limits access by competing processes to other units or volumes sharing the same controller. If other simultaneous processes need access to the same controller, some access degradation can be expected until initialization is complete; especially if you are initializing a tape cartridge in a drive that shares the root disk controller.

In general, mediainit attempts to carefully check any -f(format option) or -i(interleave options) supplied, and aborts if an option is out of range or inappropriate for the media being initialized. Specifying an interleave factor or format option value of 0 has the same effect as not specifying the option at all.

For disks that support interleave factors, the acceptable range is usually 1 (no interleave) through n − 1, where n is the number of sectors per track. Refer to the appropriate device operating manual for recommended values.

If a disk being initialized requires an interleave factor but none is speci®ed, mediainit provides an appropriate, though not necessarily optimum default.

When a given device supports format options, the allowable range of interleave factors may be related to the speci®ed format option. In such instances, mediainit cannot check the interleave factor if one is speci®ed.

Notes

Most types of mass storage media must be initialized before they can be used. HP hard disks, ¯exible disks, and cartridge tapes require some form of initialization, but 9-track tapes do not. Initialization usually involves formatting the media, writing and reading test patterns, then sparing any defective blocks. Depending upon the media and device type, none, some, or all of the initialization process may have been performed at the factory. mediainit completes whatever steps are appropriate to prepare the media for error-free operation.

Most HP hard disks are formatted and exhaustively tested at the factory by use of a process more thorough but also more time-consuming than appropriate for mediainit. However, mediainit is still valuable for ensuring the integrity of the media after factory shipment, formatting with the correct interleave factor, and sparing any blocks which may have become defective since original factory testing was performed.

HP ¯exible disks are not usually formatted prior to shipment, so they must undergo the entire initialization process before they can be used.

When a tape is certi®ed, it is thoroughly tested and defective blocks are spared. mediainit usually certi®es a tape only if it has not been certi®ed previously. If the tape has been previously certi®ed and spared, mediainit usually reorganizes the tape's spare block table, retaining any previous spares, and optimizing their assignment for maximum performance under sequential access. Reorganizing the spare block table takes only a few seconds, whereas complete certi®cation takes about a half-hour for 150-foot tapes, and over an hour for 600-foot tapes.

Reorganization of a tape's spare block table technically renders any existing data unde®ned, but the data is not usually destroyed by overwriting. To ensure that old tape data is destroyed, which is useful for secu- rity, complete tape re-certi®cation can be forced with the -roption.

HP-UX Release 11i: December 2000 − 2 − Section 1−525

m