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2.4.43 FileSfioReserveInformation

This information class is used locally to query or set reserved bandwidth for a file handle. Conceptually reserving bandwidth is effectively specifying the bytes per second to allocate to file IO.

A FILE_SFIO_RESERVE_INFORMATION data element, defined as follows, is returned to the caller.


0


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9

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1

RequestsPerPeriod

Period

RetryFailures

Discardable

Reserved

RequestSize

NumOutstandingRequests

RequestsPerPeriod (4 bytes): A 32-bit unsigned integer indicating the number of I/O requests that complete per period of time, as specified in the Period field. When setting bandwidth reservation, a value of 0 indicates to the file system that it MUST free any existing reserved bandwidth.

Period (4 bytes): A 32-bit unsigned integer that contains the period for reservation, which is the time from which I/O is issued to the kernel until the time the I/O is completed, specified in milliseconds.

RetryFailures  (1 byte): A Boolean (section 2.1.8) value.

Discardable (1 byte): A Boolean (section 2.1.8) value.

Reserved (2 bytes): Reserved for alignment. This field can contain any value and MUST be ignored.

RequestSize (4 bytes): A 32-bit unsigned integer that indicates the minimum size of any individual I/O request that can be issued by an application using bandwidth reservation. When setting reservations, this field MUST be ignored by servers and SHOULD be set to 0 by clients.

NumOutstandingRequests (4 bytes): A 32-bit unsigned integer that indicates the number of RequestSize I/O requests allowed to be outstanding at any time. When setting reservations, this field MUST be ignored by servers and SHOULD be set to 0 by clients.

This operation returns a status code as specified in section 2.2. Upon success, the status code returned by the function that processes this file information class is STATUS_SUCCESS. The most common error codes are listed in the following table.

Error code

Meaning

STATUS_NOT_SUPPORTED

0xC00000BB

The request is not supported.

STATUS_INFO_LENGTH_MISMATCH

0xC0000004

The specified information record length does not match the length that is required for the specified information class.