Processing a write request in a dispersed storage network

• US 8,966,194 B2
• Filed: 07/12/2011
• Issued: 02/24/2015
• Est. Priority Date: 10/29/2009
• Status: Expired due to Fees

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Cleversafe Incorporated (International Business Machines Corporation)
• Inventors: Resch, Jason K., Leggette, Wesley, Dhuse, Greg
• Primary Examiner(s): Rojas, Midys
• Application Number:
  US13/180,677
• Publication Number:
  US 20120030437A1
• Time in Patent Office: 1,323 Days
• Field of Search: 711/154, 711/156
• US Class Current: 711/156
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 63/08 for authentication of entities cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]
• CPC Class Codes: H04W 28/04 Error control

Abstract

A method begins by a processing module receiving a write request regarding an encoded data slice and determining whether the write request pertains to deleting the encoded data slice from a memory space. The method continues with the processing module storing a deletion marker regarding the encoded data slice when the write request pertains to deleting the encoded data slice. The method continues with the processing module determining when to delete the encoded data slice based on the deletion marker and in accordance with the deletion scheme.

Claims

1. A method comprises:

receiving a write request regarding an encoded data slice at a distributed storage unit, wherein the write request includes the encoded data slice and a value indication in a slice length field, in which a first value for the value indication indicates a write request to delete the encoded data slice from a memory space of the distributed storage unit and a second value for the value indication indicates storing of the encoded data slice in the distributed storage unit;

determining, at the distributed storage unit, whether the write request contains the first value or the second value for the value indication;

storing a deletion marker in a directory, when the write request pertains to deleting the encoded data slice;

determining when to delete the encoded data slice based on a deletion scheme, when the write request pertains to deleting the encoded data slice, deleting the encoded data slice and clearing the deletion marker once the encoded data slice is deleted; and

determining whether the encoded data slice is allowed to be stored, when the write request pertains to storing the encoded data slice, and storing the encoded data slice when storing is allowed.

2. The method of claim 1, wherein the value indication is a number, a flag or a code.

3. The method of claim 1, wherein the deletion scheme for determining when to delete the encoded data slice comprises at least one of:

deleting the encoded data slice when memory availability compares unfavorably to a memory availability threshold;

deleting the encoded data slice when a predetermined period of time has expired after receiving the write request;

deleting the encoded data slice when utilization of the memory space compares unfavorably to a memory space usage threshold; and

deleting the encoded data slice based on a deletion instruction of the write request.

4. The method of claim 1, wherein when the deletion scheme is not met, not deleting the encoded data slice.

5. The method of claim 1, wherein when determining whether the encoded data slice is allowed to be stored, determining at least one of:

indicating that storing the encoded data slice is allowable when the received encoded data slice is associated with a directory file;

indicating that storing the encoded data slice is allowable when memory availability compares favorably to a memory availability threshold; and

indicating that storing the encoded data slice is allowable when utilization of the memory space compares favorably to a memory space usage threshold.

6. The method of claim 1 further comprises:

sending an error response message in response to the write request, when the encoded data slice is not allowed to be stored when the write request pertains to storing the encoded data slice.

7. A distributed storage device comprises:

an interface;

a memory; and

a processing module operable to;

receive, via the interface, a write request regarding an encoded data slice, wherein the write request includes the encoded data slice and a value indication in a slice length field, in which a first value for the value indication indicates a write request to delete the encoded data slice from a memory space associated with the memory of the distributed storage unit and a second value for the value indication indicates storing of the encoded data slice in the memory;

determine whether the write request contains the first value or the second value for the value indication;

store a deletion marker in a directory, when the write request pertains to deleting the encoded data slice;

determine when to delete the encoded data slice based on a deletion scheme, when the write request pertains to deleting the encoded data slice, delete the encoded data slice and clear the deletion marker once the encoded data slice is deleted; and

determine whether the encoded data slice is allowed to be stored, when the write request pertains to storing the encoded data slice, and store the encoded data slice when storing is allowed.

8. The distributed storage device of claim 7, wherein the value indication is a number, a flag or a code.

9. The distributed storage device of claim 7, wherein the deletion scheme determines when to delete the encoded data slice by at least one of:

deleting the encoded data slice when memory availability compares unfavorably to a memory availability threshold;

deleting the encoded data slice when a predetermined period of time has expired after receiving the write request;

deleting the encoded data slice when utilization of the memory space compares unfavorably to a memory space usage threshold; and

deleting the encoded data slice based on a deletion instruction of the write request.

10. The distributed storage device of claim 7, wherein the processing module does not execute deletion of the encoded data slice when the deletion scheme is not met.

11. The distributed storage device of claim 7, wherein the processing module functions to determine whether the encoded data slice is allowed to be stored by at least one of:

indicating that storing the encoded data slice is allowable when the received encoded data slice is associated with a directory file;

indicating that storing the encoded data slice is allowable when memory availability compares favorably to a memory availability threshold; and

indicating that storing the encoded data slice is allowable when utilization of the memory space compares favorably to a memory space usage threshold.

12. The distributed storage device of claim 7, wherein the processing module further functions to send, via the interface, an error response message in response to the write request, when the encoded data slice is not allowed to be stored when the write request pertains to storing the encoded data slice.