File allocation control in a hard disk drive
Original Publication Date: 2002-Nov-09
Included in the Prior Art Database: 2003-Jun-21
Disclosed is a device that has control of a file allocation table (FAT) by itself. Recently consumer devices like a CAM coder utilize hard disk drives as their memory for data. For such consumer applications, low cost design is important. This new device controls files in it by itself, so that the host system does not need the file control. The features for the new hard disk drive are It accepts new commands from a host controller. The commands specify start of data stream and end of data stream. the hard disk drive handles data sent between the start command and the end command as one file. The hard disk drive has an area on its disk that has information on where the stored files are allocated. FAT area When the host requests the file information data or the file data, the hard disk drive sends the requested data to the host. Data size for moving pictures taken by the host like the CAM coder are large generally. The large data is sent to the hard disk drive as packet. The current hard disk drive does not know from which file the data is sent. Therefore the current host controller controls the file allocation on the hard disk. Making the code for the host controller is expensive as it requires extra program memory for it. For the application like the CAM coder, data sent from the host should be stored as one file, and no data for another file come from the host. Therefore if new commands are specified that tell start of data stream and end of data stream, the hard disk drive can handle data sent between the start command and the end command as one file and put the data in its unused area by itself. When the hard disk drive stores the file, it also creates the file allocation table which shows start logical block address (LBA) and end LBA for the file. The host does not need to care file allocation control, so that the host system can be inexpensive. It is important for the consumer applications. The following shows the actual flow. The hard disk receives the start data command. Then when it receives actual data, It searches unused LBA from the FAT area, and writes the data at unused LBA. When it receives the end data command, it updates the FAT area. The FAT area has information on how many files are on the disk and information on LBA positions of each file. Table.1 shows example of FAT.