Oracle VM: Manager Wrongly Shows Non-Sparse Disk As Sparse

(Doc ID 2397180.1)

Last updated on MAY 17, 2018

Applies to:

Oracle VM - Version 3.4.3 and later
Linux x86-64

Symptoms

After using Oracle VM Manager to create an ordinary non-sparse file, the type appears to revert to sparse if edited using the [EDIT] button.

Often the data in a file is not sequential: that is, some data are written at the beginning of the file, some written in the middle, and more data at the end. A sparse file scheme would not write anything in the "holes" of the file. This can accelerate disk activity since the "missing" data between the existing data chunks is not written. if an application reads the file for data where the "hole" exists, an all-zero data buffer is returned and no error is generated. Data can be written into the file where the hole is located and the new data blocks are simply added to the file and are output to the file media.

In contrast, using the traditional file space allocation would force the system to allocate disk space and insert dummy data in the "hole" between the beginning data chunk and the middle data, and between the middle data and the final data chunk. In many common scenarios that I/O activity is effectively wasted.

 

Changes

None

Cause

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