Storage apparatus and method of managing data storage area

• US 8,108,595 B2
• Filed: 07/28/2011
• Issued: 01/31/2012
• Est. Priority Date: 10/30/2008
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Araki, Akihiko, Kano, Yoshiki, Sugimoto, Sadahiro, Nonaka, Yusuke
• Primary Examiner(s): PEUGH, BRIAN R
• Application Number:
  US13/193,130
• Publication Number:
  US 20110283058A1
• Time in Patent Office: 187 Days
• Field of Search: None
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1036 Life time enhancement
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels

Abstract

To extend endurance and reduce bit cost, a method and a storage apparatus are provided, which storage apparatus includes a controller and a semiconductor storage media that includes a first storage device and a second storage device having an upper limit of an erase count of data smaller than the first storage device. Area conversion information includes correspondence of a first address to be specified as a data storage destination and a second address of an area in which data is to be stored. A rewrite frequency of stored data is recorded for each area. The controller selects an area corresponding to the first address, determines whether or not the rewrite frequency of the selected area is equal to or larger than a first threshold value, when the rewrite frequency is equal to or larger than the threshold value, selects an area to be provided by the first storage device, and when the rewrite frequency is smaller than the threshold value, selects an area to be provided by the second storage device and maps the address of the selected area to the first address.

Claims

1. A storage apparatus comprising:

a first flash memory device in which an acceptable erase count is limited,

a second flash memory device in which an acceptable erase count is lower than that of the first flash memory device, and

a controller configured to copy data of a first area in the first flash memory device to a second area in the second flash memory device on the basis of a rewrite frequency of the first area.

2. A storage apparatus according to claim 1,

wherein the controller is configured to update a relation between a logical address corresponding to the data and a first address corresponding to the first area to a relation between the logical address and a second address corresponding to the second area.

3. A storage apparatus according to claim 1,

wherein the controller is configured to copy the data of the first area to the second area when the rewrite frequency is higher than a threshold value.

4. A storage apparatus according to claim 3,

wherein the controller is configured to copy the data of the first area to a third area in the first flash memory device when the rewrite frequency is lower than the threshold value.

5. A storage apparatus according to claim 4,

wherein the rewrite frequency is a number corresponding to an erase count for a predetermined period.

6. A storage apparatus according to claim 1,

wherein the first flash memory device comprises a single level cell flash memory device, and the second flash memory device comprises a multi level cell flash memory device.

7. A method for copying data in a storage apparatus including a first flash memory device in which an acceptable erase count is limited, and a second flash memory device in which an acceptable erase count is lower than that of the first flash memory device, the method comprising:

copying data of a first area in the first flash memory device to a second area in the second flash memory device on the basis of a rewrite frequency of the first area.

8. A method according to claim 7, the method further comprising updating a relation between a logical address corresponding to the data and a first address corresponding to the first area to a relation between the logical address and a second address corresponding to the second area.

9. A storage apparatus according to claim 7, further comprising copying the data of the first area to the second area when the rewrite frequency is higher than a threshold value.

10. A storage apparatus according to claim 9, further comprising copying the data of the first area to a third area in the first flash memory device when the rewrite frequency is lower than the threshold value.

11. A storage apparatus according to claim 10,

wherein the rewrite frequency is a number corresponding to an erase count for a predetermined period.

12. A storage apparatus according to claim 7,

wherein the first flash memory device comprises a single level cell flash memory device, and the second flash memory device comprises a multi level cell flash memory device.