US 8,818,966 B1Granted

Continuous file defragmentation during file over-writes

AssigneeEMC Corporation

InventorKumari Bijayalaxmi Nanda

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Abstract

When a file system manager responds to a request to write data to a specified number of blocks of a file, the file system manager determines that corresponding file system data block allocations exist and determines that the file is fragmented over the corresponding file system data block allocations. In response to determining that the file is fragmented over the corresponding file system data block allocations, the file system manager allocates and substitutes a single extent of contiguous file system data blocks for the corresponding file system data block allocations, and writes data to the newly allocated contiguous file system data blocks. For example, the file system manager compares a spread and a count of extent fragments of the file system data block allocations to appropriate thresholds to trigger the defragmentation upon file over-write.

Claims20

Dependent claims

A method of reducing fragmentation of a file when writing to the file in a digital computer, said method comprising a data processor of the digital computer executing computer instructions stored in a non-transitory computer readable storage medium to perform the steps of:

(a) responding to a request to write data to a specified number of blocks in a logical extent of the file beginning at a specified offset in the logical extent of the file by determining whether or not file system block allocations exist for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file;
and
(b) upon determining in step (a) that file system block allocations exist for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file, obtaining a measure of the fragmentation of the file over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, and based on the measure of fragmentation of the file over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, determining that the file is fragmented over the file system block allocations for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file;
and
(c) in response to determining in step (b) that the file is fragmented over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, allocating a single extent of a number of contiguous file system blocks equal to the specified number, writing the specified number of blocks of data to the specified number of the contiguous file system blocks in the newly allocated single extent, and substituting the specified number of the contiguous file system blocks in the newly allocated single extent for the file system block allocations for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file, in order to reduce the fragmentation of the file.

2 more elements

A file server comprising a data processor and non-transitory computer readable storage medium storing computer instructions that, when executed by the data processor, perform the steps of:

(a) responding to a request to write data to a specified number of blocks in a logical extent of a file beginning at a specified offset in the logical extent of the file by determining whether or not file system block allocations exist for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file;
and
(b) upon determining in step (a) that file system block allocations exist for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file, obtaining a measure of fragmentation of the file over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, and based on the measure of fragmentation of the file over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, determining that the file is fragmented over the file system block allocations for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file;
and
(c) in response to determining in step (b) that the file is fragmented over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, allocating a single extent of a number of contiguous file system blocks equal to the specified number, writing the specified number of blocks of data to the specified number of the contiguous file system blocks in the newly allocated single extent, and substituting the specified number of the contiguous file system blocks in the newly allocated single extent for the file system block allocations for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file, in order to reduce the fragmentation of the file.

2 more elements

A non-transitory computer readable storage medium storing computer instructions that, when executed by a data processor, perform the steps of:

(a) responding to a request to write data to a specified number of blocks in a logical extent of a file beginning at a specified offset in the logical extent of the file by determining whether or not file system block allocations exist for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file;
and
(b) upon determining in step (a) that file system block allocations exist for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file, obtaining a measure of fragmentation of the file over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, and based on the measure of fragmentation of the file over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, determining that the file is fragmented over the file system block allocations for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file;
and
(c) in response to determining in step (b) that the file is fragmented over the file system block allocations for the specified number of blocks of the file beginning at the specified offset in the logical extent of the file, allocating a single extent of a number of contiguous file system blocks equal to the specified number, writing the specified number of blocks of data to the specified number of the contiguous file system blocks in the newly allocated single extent, and substituting the specified number of the contiguous file system blocks in the newly allocated single extent for the file system block allocations for the specified number of blocks in the logical extent of the file beginning at the specified offset in the logical extent of the file, in order to reduce the fragmentation of the file.

2 more elements

Dependencies are inferred from the claim text.