Managing data storage space on large capacity record media

Claim 2

A data storage system for storing and retrieving data with respect to a record medium which has, potentially, a large multiplicity of addressable rewritable data storage areas but which is initially presented as an unformatted entity, the system including means for formatting portions of the medium and for reading and writing data in formatted storage areas under the control of a local or remote processor, the system being arranged to maintain a volume table of contents (VTOC) recorded on the medium for indicating the status and the data contents of the medium, including which storage areas are allocated ones of the addressable data storage areas; which storage areas are unallocated ones of the addressable data storage areas that are still storing data; and which potential storage areas are unformatted ones of the addressable data storage areas that cannot receive data for storage until predetermined format signals are recorded therein and, by reference to the VTOC, to progressively format the record medium between accesses thereto.

Claim 3

A system as claimed in claim 1, wherein the medium cannot be overwritten so that previously written storage areas must be erased before they can be rewritten, means are provided for erasing allocated written storage areas between accesses and the VTOC is updated to also show which allocated ones of the addressable storage areas have been erased.

Claim 6

A system as claimed in claim 4, wherein each of the record tracks has a single index indicia and includes one of the addressable data storage areas, each formatted track having a home address record in immediate juxtaposition to the respective index mark, which home address record contains the rotational locations of defects in the respective record tracks, the unformatted tracks having no home address record.

Claim 7

A system as claimed in claim 5, wherein each track has an indication of the circular extent of the track and the initialising of the record disk for data recording, whether for the initial radially outward set of a predetermined number of the tracks or subsequent outwardly located tracks as becomes possible, is by surface analysing such tracks and recording the location and extent of each detected surface defect on the respective track; and updating the VTOC both as to the allocation of such initialised tracks and as to the now limit one of the uninitialised tracks, subsequent initialisation beginning at the limit track so recorded.

Claim 8

A system as claimed in claim 6, wherein allocated tracks for which the data stored thereon is no longer required are deallocated, the VTOC being updated accordingly, the control processor being arranged, when the disk is not being used for receiving signals to be recorded on the disk or for supplying recorded signals from the disk, to erase the deallocated - free - but not erased tracks, updating the VTOC accordingly; and to delaying initialising additional ones of the unformatted tracks until all of the free but not erased tracks have been erased.

Claim 9

A system as claimed in claim 7, wherein any erasing and/or formatting operation performed when the disk is not being used, are limited to one track per operation and are interleaved between data recording and data readback operations, but, if the disk is such that erasing before recording is required - there being no overwrite possibility - and writing into track is requested to update a record which is substantially less than the extent of a record track, such writing is delayed while immediate erasing of the portion to be updated is performed, whereas, if the whole of a record already recorded is presented for storing, the update is recorded in free record areas and the tracks appropriate to the prior version are deallocated and subsequently erased.

Claim 11

In a data storage subsystem having a control unit including program means for operating the control unit and the subsystem, a disk recorder operatively coupled to the control unit and having a large capacity disk recording surface; operating program means including a program dispatcher in the control unit for effecting subsystem operation which includes recording data onto the large capacity disk surface and reading data recorded on the disk surface; formatting program means in the control unit, including surface analysis controlling program means and home address recording program means which records locations of defects in a respective track in a home address record in such track; the dispatcher having initialisation programming means operative to cause the control unit to check the large capacity disk surface to determine whether or not the disk surface has been initialised, and if not initialised, operative to activate the formatting program means a given plurality of times for surface analysing and formatting a predetermined number of record tracks at a radial outward portion thereof and recording a volume table of contents (VTOC) in a radial outward most one of the predetermined set of tracks; the dispatcher having further intermediate format initiating program means activated when the large capacity disk surface is not currently primed for recording or supplying readback signals from and to the control unit for activating the formatting program means to format a second predetermined number of the unformatted record tracks, beginning with a radially outermost one of the unformatted record tracks; the dispatcher cycling through all of its operations such that the intermediate formatted program means is activated as a lower priority one of operations to be performed in the subsystem; the intermediate formatting means selects a single record track to be surface analysed and formatted by the formatting program means; erasure program means in the control unit actuable by the dispatcher program means whenever the large capacity disk surface is not primed for recording data signals or supplying readback data signals for erasing data tracks on the large capacity disk surface which are not indicated as being used for data recording; allocation program means in the control unit for allocating ones of the record tracks for receiving data signals and indicating to the allocated ones of the record track as being used for data recording and including means for recording the status of the tracks in the VTOC; the dispatcher giving the erasure program means priority over the intermediate formatting program means; and program means in the control unit actuable by the dispatcher to allocate a free and erased track to receive updated data for recording and maintaining the same addressability for the updated data as is established for the originally recorded data. the reallocating program means actuating the erasure programming means for erasing the old data track after the newly allocated record track has received the updated data.

Claim 12

In a data storage subsystem having a control unit including program means for operating the control unit and the subsystem, a disk recorder operatively coupled to the control unit and having a large capacity disk recording surface; operating program means including a program dispatcher in the control unit for effecting subsystem operation which includes recording data onto the large capacity disk surface and reading data recorded on the disk surface; formatting program means in the control unit, including surface analysis controlling program means and home address recording program means which records locations of defects in a respective track in a home address record in such track; the dispatcher having initialisation programming means operative to cause the control unit to check the large capacity disk surface to determine whether or not the disk surface has been initialised, and if not initialised, operative to activate the formatting program means a given plurality of times for surface analysing and formatting a predetermined number of record tracks at a radial outward portion thereof and recording a volume table of contents (VTOC) in a radial outward most one of the predetermined set of tracks; the dispatcher having further intermediate format initiating program means activated when the large capacity disk surface is not currently primed for recording or supplying readback signals from and to the control unit for activating the formatting program means to format a second predetermined number of the unformatted record tracks, beginning with a radially outermost one of the unformatted record tracks; the dispatcher cycling through all of its operations such that the intermediate formatted program means is activated as a lower priority one of operations to be performed in the subsystem; the intermediate formatting means selects a single record track to be surface analysed and formatted by the formatting program means; erasure program means in the control unit actuable by the dispatcher program means whenever the large capacity disk surface is not primed for recording data signals or supplying readback data signals for erasing data tracks on the large capacity disk surface which are not indicated as being used for data recording; allocation program means in the control unit for allocating ones of the record tracks for receiving data signals and indicating to the allocated ones of the record track as being used for data recording and including means for recording the status of the tracks in the VTOC; the dispatcher giving the erasure program means priority over the intermediate formatting program means; and program means in the control unit actuable by the dispatcher to allocate a free and erased track to receive updated data for recording and maintaining the same addressability for the updated data as is established for the originally recorded data. the reallocating program means actuating the erasure programming means for erasing the old data track after the newly allocated record track has received the updated data.