System and method for retention of historical data in storage resources

• US 8,949,553 B2
• Filed: 10/28/2011
• Issued: 02/03/2015
• Est. Priority Date: 10/28/2011
• Status: Active Grant

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Kotzur, Gary B., Brahmaroutu, Surender
• Primary Examiner(s): Faal, Baboucarr
• Application Number:
  US13/283,911
• Publication Number:
  US 20130111161A1
• Time in Patent Office: 1,194 Days
• US Class Current: 711/154
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7209 Validity control, e.g. using flags, time stamps or sequence numbers

Abstract

In accordance with embodiments of the present disclosure, a method may include receiving a read command. The method may also include determining if the read command is a command to read current data or historical data for a given logical address. The method may additionally include reading data stored on a storage resource at a historical physical address defined by a historical data offset associated with the given logical address in response to determining that the read command is a command to read historical data. The method may further include communicating the data stored at the historical physical address as a response to the read command.

Claims

1. A system comprising a storage controller operatively coupled with a non-transitory computer readable medium, the non-transitory computer readable medium including:

a retention mode variable indicating whether the storage controller is configured to retain stale data stored on the non-transitory computer readable medium;

an address mapping table, the mapping table comprising;

one or more entries, each entry associating a logical address with a corresponding physical address;

for each physical address, a stale variable indicating whether data stored at the physical address is stale;

for each physical address, a retain variable indicating whether data stored at the physical address is to be retained if data stored at the physical address is stale; and

for each logical address, a historical data offset, indicating a second physical address at which historical data associated with the logical address is located.

2. A system according to claim 1, the storage controller configured to, in response to a read command received by the storage controller:

determine if the read command is a command to read current data or historical data for a given logical address;

return current data for the given logical address from the physical address indicated to be associated with the given logical address in the mapping table in response to determining the read command is a command to read current data; and

return historical data associated with the logical address indicated to be associated with the given virtual address in the mapping table from a physical address indicated by the historical data offset in response to determining the read command is a command to read historical data.

3. A system according to claim 1, the storage controller configured to, in response to a write command received by the storage controller:

determine if data exists at a physical address associated with a logical address of the write command;

determine if the retention mode variable is set; and

retain historical data associated with the logical address by setting the stale variable associated with the physical address and setting the retain variable associated with the physical address in response to determining that data exists at the physical address and determining that the retention mode variable is set.

4. A system according to claim 3, the storage controller further configured to:

save data associated with the write command to a second physical address; and

update the mapping data to indicate the association between the logical address and the second physical address.

5. A system according to claim 1, the storage controller configured to in response to a command to perform a release operation received by the storage resource, release data stored at a physical address associated with the command by clearing the retain variable associated with the physical address.

6. A system according to claim 1, the storage controller configured to, when performing garbage collection and data reclamation on storage media of the storage resource:

perform garbage collection and data reclamation for addresses in which the retain variable is cleared; and

defer garbage collection and data reclamation for addresses in which the retain variable is enabled.

7. A system according to claim 1, the non-transitory computer readable medium comprising a solid-state storage device.

8. A system according to claim 1, the logical addresses comprising logical block addresses and the physical addresses comprising physical block addresses.

10. A method according to claim 4, further comprising:

saving data associated with the write command to a second physical address; and

updating a mapping data to indicate the association between the virtual address and the second physical address.

9. A method comprising:

receiving a write command;

determining if data exists at a physical address associated a logical address of the write command;

determining if a retention mode variable is set, the retention mode variable indicating whether a storage resource is configured to retain stale data stored on the storage resource; and

retaining historical data associated with the physical address by setting a stale variable associated with the physical address and setting a retain variable associated with the physical address in response to determining that data exists at the physical address and determining that the retention mode variable is set.