ICC-NCQ Command Scheduling for Shingle-written Magnetic Recording (SMR) Drives

A method of operating an SMR data storage device the method comprising:

• adding a write command with data received from a host to a command queue, the command queue already having at least one previously received command stored therein;
• determining a set of subcommands required to write all of the LBAs, estimating a completion time for the write command by adding together estimated completion times for the set of subcommands;
• and
• selecting a next command from the command queue for execution based at least in part on the completion time for the write command.

An SMR data storage device comprising:

• a set of storage regions including write-twice cache regions, E-regions and I-regions;
• an indirection system that maps LBAs in host commands to write-twice cache regions, E-regions and I-regions;
• and
• a command processor that receives read and write commands from a host specifying LBAs and stores the read and write commands in a command queue, the command processor including means for determining using the indirection system whether the command requires accessing one or more of the write-twice cache regions, E-regions or I-regions, determining a set of subcommands required to complete each command, estimating a completion time for each command by adding together estimated completion times for the set of subcommands, and selecting a next command for execution based at least in part on the completion time for each command in the queue.