Adjustable threshold for buffer management

An apparatus for the storage of data comprising:

• an electronic buffer adapted for connection between a host computer and a tape on which data is recorded, said buffer being for temporarily storing data transferred between the host computer and the tape, and said buffer having a threshold level for determining the amount of data in said buffer which initiates the mechanical movement of the tape so that the tape can ramp up to the velocity at which it can transfer data between the tape and said buffer, either through a write or a rear operation;
• transmission delaying means, responsive to the amount of data in said buffer, for delaying the transmission of data between the host computer and said apparatus;
• and
• means for responsively adjusting said threshold level, said adjustment being made on the basis of the occurrence or nonoccurrence of a data transmission delay between the host computer and said apparatus.

An apparatus for storing data, said apparatus adapted for connection to a host node for the host node to read data from or write data to said apparatus, and said apparatus adapted for delaying the transmission of data through a read or write transaction, said apparatus comprising:

• means for recording data, said recording means requiring some period of time ("t") after said recording means is signaled to initiate a read or write operation to actually perform the read or write operation, where t is greater than the amount of time it takes for a storing means coupled to said recording means to receive data from either the host node or said recording means;
• means for temporarily storing data coupled to said recording means, said storing means having a threshold level for determining the amount of data in said storing means which initiates a transfer of data to or from said recording means, either through a write or read operation;
• means for controlling the operation of said storing means and said recording means, said controlling means being for signaling to said recording means to initiate a read or write operation;
• and
• means for responsively adjusting said threshold level, the adjustment being made on the basis of the occurrence or nonoccurrence of a delay in the transmission of data between said apparatus and the host node.

An apparatus for the storage of data, said apparatus comprising:

• storing means adapted for connection between a host node and a data recording means for temporarily storing data transferred between the host node and the recording means, said storing means having a threshold level for determining the amount of data in said storing means which initiates a transfer of data to or from the recording means, either through a write or read operation;
• transmission delaying means, responsive to the amount of data in said storing means, for delaying the transmission of data between the host node and said apparatus;
• and
• means for responsively adjusting said threshold level, the adjustment being made on the basis of the occurrence or nonoccurrence of a data transmission delay between the host node and said apparatus.

A method for establishing and adjusting threshold level for an electronic buffer in a tape drive, said buffer being a means for temporarily storing data written by a host computer to the tape, and said threshold level being for determining the amount of data in the buffer which initiates the mechanical movement of the tape to ramp up to the velocity of which the tape can receive data transferred from the buffer to the tape, said method comprising the steps of:

• establishing a threshold level for the buffer at the commencement of the first write transaction after the tape drive is powered up;
• temporarily storing data written by the host computer to the tape drive in the buffer;
• ramping up the tape to its write velocity as soon as the amount of data in the buffer reaches the threshold level;
• testing whether the tape drive caused the host computer to delay the transfer of data to the tape drive at any time since the buffer was last empty;
• writing all of the data from the buffer to the tape as soon as the tape has reached its write velocity;
• adjusting the previously established threshold level upwards if at the time the data began being written out of the buffer the tape drive had not delayed the transmission of data to the host computer the delay occurring at any time since the buffer was last empty;
• adjusting the previously established threshold level downwards if at the time the data began being written out of the buffer the tape drive had delayed the transmission of data to the host computer, the delay occurring at any time since the buffer was last empty;
• and
• repositioning the tape for a subsequent write operation.

A method for establishing and adjusting a threshold level for an electronic buffer in a tape drive, said buffer being a means for temporarily storing data read by a host computer from a tape, and said threshold level being for determining the amount of data in the buffer which initiates the mechanical movement of the tape to ramp up the tape to the velocity at which the tape can transfer data from the tape into the buffer, said method comprising the steps of:

• establishing a threshold level for the buffer at the commencement of the first read transaction after the tape drive is powered up;
• temporarily storing data read by the host computer from the tape drive in the buffer;
• ramping up the tape to its write velocity as soon as data stored in the buffer reaches the threshold level;
• testing whether the tape drive delayed the transmission of data to the host computer at any time since the buffer was last filled;
• transferring all of the data from the buffer to the host computer through a read operation;
• adjusting the previously established threshold level downward if at the time the data began being read from the buffer by the host computer the tape drive had not delayed the transmission of data to the host computer, the delay occurring at any time since the buffer was last filled;
• adjusting the previously established watermark upwards if at the time the data began being read from the buffer by the host computer the tape drive had delayed the transmission of data to the host computer, the delay occurring at any time since the buffer was last filled;
• and
• repositioning the tape for a subsequent read operation.

A tape drive for storing data on a tape, and adapted for delaying the transmission of data through a read or write transaction in the event that a host computer, which is coupled to the tape drive, is ready to transfer data to or from said tape drive through one of a series of data transfer operations, but said tape drive is not ready to perform the transfer operation, said tape drive comprising:

• a tape on which data is recorded, said tape being mechanically moved to effect a data transfer to and from the host computer;
• an electronic buffer for temporarily storing data, said buffer adapted for coupling between said tape and the host computer;
• means for establishing a threshold level within said buffer, said threshold level being the amount of data in said buffer which initiates the mechanical movement of said tape so that said tape can ramp up to the velocity at which data can transferred between said tape and said buffer;
• and
• means for adjusting said threshold level for said buffer in response to the occurrence or nonoccurrence of a delay in the transmission of data between the host computer and said tape drive during a previous data transfer.