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EP0455922A2
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EP
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Method and apparatus for deriving mirrored unit state when re-initializing a system
Assignee: International Business Machines Corp
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Filing: 1990-12-28
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Granted: —
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Expires: 2010-12-28
Abstract
Abstract A data processing system having a pair of mirrored storage units (121, 131) maintains a state record of the mirrored pair in system memory (103). In order to be able to determine state when the system is re-initialized, this state information is also stored on each storage unit of the mirrored pair, and in an alternate location (104). When the state changes, the operating system writes the new state to those storage units which are still functioning, and to the alternate location. In order to prevent ambiguous situations, only certain defined state transitions are permitted. When the system is re-initialized, it attempts to read the state information stored on the storage units. If either unit can not be read, the system substitutes the state retrieved from the alternate state record for the state that would have been read from the non-responding unit. This pair of states from the two units index an unique entry in a state derivation table containing the resultant state.
Inventors
- 👤 Kenneth James Lawrence
- 👤 Michael James Mcdermott
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 17:00
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/16; G06F11/1666; G06F11/14; G06F11/1402; G06F11/1415; G06F11/1417; G11; G11C; G11C29/00; G11C29/70; G11C29/74; G06F11/20
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
142 words
A method for determining the state of a mirrored pair of data storage units in a data processing system, comprising the steps of: retrieving a first state record from a first storage unit of said mirrored pair of storage units to obtain a state associated with said first storage unit; retrieving a second state record from a second storage unit of said mirrored pair of storage units to obtain a state associated with said second storage unit; retrieving an alternate state record from an alternate location; substituting state information contained in said alternate state record for the state associated with one of the storage units if it is not possible to retrieve the state record from the storage unit; and determining the resultant state of said mirrored pair corresponding to the pair of states associated with said first and second storage units.
Claim 2
Dependent Claim
58 words
The method for determining the state of a mirrored pair of data storage units of claim 1, wherein said step of determining the state of said mirrored pair comprises retrieving the state of said mirrored pair from an entry in a state derivation table corresponding to the pair of states associated with said first and second storage units.
Claim 3
Dependent Claim
29 words
The method for determining the state of a mirrored pair of data storage units of claim 1, wherein said alternate state record is retrieved from non-volatile random access memory.
Claim 4
Dependent Claim
29 words
The method for determining the state of a mirrored pair of data storage units of claim 2, wherein said alternate state record is retrieved from non-volatile random access memory.
Claim 5
Independent Claim
214 words
A method for determining the states of the mirrored pairs of data storage units in a data processing system having at least two mirrored pairs of storage units, comprising the steps of: retrieving a first state record from a first storage unit of a first mirrored pair of storage units to obtain a state associated with said first storage unit; retrieving a second state record from a second storage unit of said first mirrored pair of storage units to obtain a state associated with said second storage unit; retrieving an alternate state record from an alternate location; substituting state information contained in said alternate state record for the state associated with one of the storage units of said first mirrored pair of storage units if it is not possible to retrieve the state record from the storage unit; determining the state of said first mirrored pair by determining the state corresponding to the pair of states associated with said first and second storage units of said first mirrored pair; and retrieving the state of each mirrored pair of storage units other that said first mirrored pair from any storage unit of said first mirrored pair which is determined, by said step of determining the state of said first mirrored pair, to have current data.
Claim 6
Dependent Claim
65 words
The method for determining the state of a mirrored pair of data storage units of claim 5, wherein said step of determining the state of said first mirrored pair comprises retrieving the state of said first mirrored pair from an entry in a state derivation table corresponding to the pair of states associated with said first and second storage units of said first mirrored pair.
Claim 7
Dependent Claim
29 words
The method for determining the states of the mirrored pairs of data storage units of claim 6, wherein said alternate state record is retrieved from non-volatile random access memory.
Claim 8
Dependent Claim
29 words
The method for determining the states of the mirrored pairs of data storage units of claim 7, wherein said alternate state record is retrieved from non-volatile random access memory.
Claim 9
Dependent Claim
161 words
A data storage apparatus for a data processing system having a mirrored pair of data storage units, comprising: a first storage unit of said mirrored pair, having a state record for storing the state of said mirrored pair; a second storage unit of said mirrored pair, having a state record for storing the state of said mirrored pair; state retrieval means, coupled to said first and second storage units, for retrieving the stored state records of said first and second storage units; and state determination means, coupled to said state retrieval means, for determining the state of said mirrored pair of data storage units when the data processing system is re-initialized, wherein said state determination means determines the state of said mirrored pair when the state record retrieved from one of the storage units indicates that both storage units of said mirrored pair contain current data, and it is not possible to retrieve the state record from the other storage unit.
Claim 10
Dependent Claim
51 words
The data storage apparatus of claim 9, wherein said state determination means comprises means for substituting the state information contained in an alternate state record for the state information contained on one of the storage units in the event the state information contained on the storage unit can not be retrieved.
Claim 11
Dependent Claim
82 words
The storage apparatus of claim 10, wherein the state determination means further comprises a state derivation table having a unique state entry corresponding to each possible pair of a state associated with the first storage unit and a state associated with the second storage unit, whereby the state of said mirrored pair is determined by retrieving from said state derivation table the entry corresponding to the state associated with said first storage unit and the state associated with said second storage unit.
Claim 12
Dependent Claim
65 words
The data storage apparatus of claim 11, further comprising: a third storage unit for storing data; a fourth storage unit for storing a copy of the data stored on said third storage unit; wherein said state determination means automatically determines the states of said third and fourth storage units using the information contained in the state records stored on said first and second storage units.
References Cited (Backward Citations)
No citation records indexed.
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