Class TVolumeIOParamInfo

class TVolumeIOParamInfo;

Description

Volume IO parameter information.

This class is used to query IO parameters including block size, cluster size, etc on a certain volume.

These parameters are essential to user to assist in chosing efficient size of buffers for reading and writing.

Members

Defined in TVolumeIOParamInfo:
iBlockSize, iClusterSize, iRecReadBufSize, iRecWriteBufSize

TInt iBlockSize;

Description

Read and write operations on certain underlying media are done in blocks. A write operation that modifies only part of a block will be less efficient, in general, than one that modifies an entire block. Data throughput degrades linearly for reads or writes in smaller sized units. Reads and writes aligned on block boundaries are up to two times faster than when mis-aligned.

TInt iClusterSize;

Description

The size in bytes of a single disk cluster. The file system organises and allocates the file data on the disk in clusters where each cluster is one or more blocks. Files which are not zero length will occupy at least one cluster of the disk, so large numbers of very small files can use up more disk space than expected. Reads and writes aligned on cluster boundaries are more efficient.

TInt iRecReadBufSize;

Description

A recommanded value of buffer size on certain drives for optimized reading performance. The figure is based on sensible benchmark testing results. Mobile device vendors should run those tests and provide this information by attach the drive name, variable name and value in estart.txt file. An example is shown below to indicate the format in which the information text should be represented in estart.txt:

[DriveC] RecReadBufSize 8192

When there is no such value provided, value KErrNotSupported should be returned.

TInt iRecWriteBufSize;

Description

A recommanded value of buffer size on certain drives for optimized writing performance. The figure is based on sensible benchmark testing results. Mobile device vendors should run those tests and provide this information by attach the drive name, variable name and value in estart.txt file. An example is shown below to indicate the format in which the information text should be represented in estart.txt:

[DriveC] RecWriteBufSize 16384

When there is no such value provided, value KErrNotSupported should bereturned.