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Increased Efficiency during Initialization of Global Metadata Structures Disclosure Number: IPCOM000032418D
Original Publication Date: 2004-Nov-04
Included in the Prior Art Database: 2004-Nov-04
Document File: 1 page(s) / 26K

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The invention involves using a specific opcode in the journal to indicate that a structure needs to be initialized. By using this opcode instead of storing the entire initialized structure, a considerable amount of journal space is saved.

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Increased Efficiency during Initialization of Global Metadata Structures

Disclosed is a method for journaling the initialization of a structure in Global Metadata using a unique opcode. Global Metadata is an area on disk used to store control structures. The journal is a non-volatile method of storing data until it is destaged to disk. The journal is used to recover the data in case there is a power outage before the data is destaged. It is sometimes necessary to initialize a structure in Global Metadata with default values. The current method writes the entire initialized structure to the journal. There is a limit of the amount of data which can be written to the journal in a single update. This limit can be less than the size of some structures which exists on disk. This means that writing a large structure to the journal can require multiple updates. In addition, filling the journal quickly has a negative impact on performance, so journal updates should always be kept as small as possible.

For the disclosed method, when a structure on disk requires initialization, an opcode is stored in the journal instead of the entire initialized structure. By this opcode, it is known which strucuture is being initialized and what default values need to be placed in the structure. If a power loss occurs before the structure is written to disk, this opcode is read from the journal as part of the recovery process. When the opcode is seen, the structure is written to disk with...