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Improving the performance score of multi-thread sequential read

IP.com Disclosure Number: IPCOM000013436D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 1 page(s) / 27K

Publishing Venue

IBM

Abstract

Disclosed is a method to improve the performance score of multi-thread sequential read operation of HDD (Hard Disk Drive). The performance score of multi-thread sequential read operation is much less than the value of the thread number times the performance score of single thread sequential read operation, because seek operations must be done to switch from a thread to another. It is very effective to reduce the number of seek operations in order to improve the performance of multi-thread sequential read operation. The firmware, which may be called also Microcode, can analyze the command sequence, and it can detect multi-thread read access. For example under multi-segmented sector buffer architecture, the firmware can save the last accessed LBA (Logical Block Address) for each segment. When a read command is issued, the firmware searches the saved LBAs to examine whether the command is a sequential read to one of previously processed read commands or a random access read. Another example under non-segmented sector buffer architecture, the firmware can keep command history. When a read command is issued, the firmware searches the LBAs in the command history to detect sequential access. When more than two sequential threads are detected, the firmware does look-ahead operation with queued commands waiting for execution. During multi-thread sequential read operation, the next command to execute is not a sequentially accessing one in general. But the look-ahead data read into the buffer will be accessed later by a few sequentially accessing read commands, because the size of a segment buffer is much larger than the read length of each read command usually, In this way a read operation from the media can set up enough data in the sector buffer for multiple sequentially accessing read commands of a thread. 1

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Improving the performance score of multi-thread sequential read

    Disclosed is a method to improve the performance score of multi-thread sequential read operation
of HDD (Hard Disk Drive). The performance score of multi-thread sequential read operation is much
less than the value of the thread number times the performance score of single thread sequential read
operation, because seek operations must be done to switch from a thread to another. It is very
effective to reduce the number of seek operations in order to improve the performance of multi-thread
sequential read operation.

The firmware, which may be called also Microcode, can analyze the command sequence, and it can detect
multi-thread read access. For example under multi-segmented sector buffer architecture, the firmware
can save the last accessed LBA (Logical Block Address) for each segment. When a read command is
issued, the firmware searches the saved LBAs to examine whether the command is a sequential read to
one of previously processed read commands or a random access read. Another example under
non-segmented sector buffer architecture, the firmware can keep command history. When a read command
is issued, the firmware searches the LBAs in the command history to detect sequential access.

When more than two sequential threads are detected, the firmware does look-ahead operation with
queued commands waiting for execution. During multi-thread sequential read operation, the next
command to execute is not a sequentially...