Native snapshots in distributed file systems

• US 10,262,004 B2
• Filed: 02/29/2016
• Issued: 04/16/2019
• Est. Priority Date: 02/29/2016
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Inventors: Bellur, Vijay
• Primary Examiner(s): Cao, Phuong Thao
• Application Number:
  US15/056,962
• Publication Number:
  US 20170249216A1
• Time in Patent Office: 1,142 Days
• Field of Search: 707649
• CPC Class Codes: G06F 11/1446 Point-in-time backing up or restoration of persistent data
• CPC Class Codes: G06F 16/128 Details of file system snapshots on the file-level, e.g. snapshot creation, administration, deletion use of snapshots for error detection or correction G06F11/14, G06F11/16
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: G06F 3/06 Digital input from, or digital output to, record carriers , e.g. RAID, emulated record carriers or networked record carriers
• CPC Class Codes: G06F 3/065 Replication mechanisms

Abstract

Methods and systems are disclosed to initiate a snapshot of a volume distributed across a plurality of storage nodes of a distributed file system. The systems may create in the plurality of storage nodes a writeable sub-volume associated with the volume of the distributed file system. The system may identify a previous writeable sub-volume associated with a previous snapshot and mark the previous writeable sub-volume as read-only.

Claims

1. A method comprising:

generating, by a processing device, a first writeable sub-volume associated with a first snapshot of a volume distributed across a plurality of storage nodes of a distributed file system;

identifying, by the processing device, a second writeable sub-volume associated with a second snapshot of the volume taken prior to the first snapshot;

marking, by the processing device, the second writeable sub-volume of the distributed file system as read-only;

initiating a reversion to a snapshot revert point of the volume;

identifying a read-only sub-volume associated with the snapshot revert point;

identifying a plurality of read-only sub-volumes associated with snapshots taken more recently than the snapshot revert point;

removing the first writeable sub-volume and the plurality of read-only sub volumes; and

marking the read-only volume associated with the snapshot revert point as writeable.

2. The method of claim 1, further comprising:

initiating, by the processing device, a second snapshot of the volume of the distributed file system;

creating, by the processing device, a third writeable sub-volume associated with the volume of the distributed file system; and

marking, by the processing device, the first writable sub-volume associated with the distributed file system as read-only.

3. The method of claim 1, further comprising:

initiating a deletion of a snapshot for deletion from the distributed file system;

copying a first read-only sub-volume associated with the snapshot for deletion to a second read-only sub-volume associated with a snapshot taken subsequent to the snapshot for deletion; and

removing the first read-only sub-volume associated with the snapshot for deletion from the distributed file system.

4. The method of claim 1, further comprising:

receiving an instruction to perform a write operation for an object in the volume;

determining that the object is in a read-only sub-volume associated with the volume;

copying the object from the read-only sub-volume to the first writeable sub-volume; and

performing the write operation on the object in the first writeable sub-volume.

5. The method of claim 1, further comprising:

receiving an instruction to perform a deletion of an object in the volume;

determining that the object exists in a read-only sub-volume associated with the volume; and

generating a negative entry for the object in the first writeable sub-volume.

6. The method of claim 5, further comprising:

receiving an instruction to perform a read on the object in the volume;

generating an error in response to determining that the negative entry exists for the object; and

returning the error to a client device that provided the instruction.

7. The method of claim 1, wherein the first snapshot enables the distributed file system to revert to a corresponding snapshot reversion point.

8. A system comprising:

a memory; and

a processing device operatively coupled to the memory, the processing device to;

create, by the processing device, a first writeable sub-volume associated with a volume distributed across a plurality of storage nodes of a distributed file system;

identify, by the processing device, a second writeable sub-volume associated with a previous snapshot;

mark, by the processing device, the second writeable sub-volume of the distributed file system as read-only;

receive an instruction to perform a write operation for an object in the volume;

determine that the object is in a read-only sub-volume associated with the volume;

copy a partition of the object from the read-only sub-volume to the first writeable sub-volume; and

perform the write operation on the partition of the object in the first writeable sub-volume.

9. The system of claim 8, wherein the processing device is to create the first writeable sub-volume in response to receiving a request to generate a snapshot.

10. The system of claim 8, wherein the processing device is further to:

identify a first read-only sub-volume associated with a snapshot for deletion;

identify a second read-only sub-volume, wherein the second read-only sub-volume is associated with a snapshot taken subsequent to the snapshot for deletion;

copy the first read-only sub-volume to the second read-only sub-volume; and

remove the first read-only sub-volume from the distributed file system.

11. The system of claim 8, wherein the processing device is further to:

identify a first read-only sub-volume associated with a snapshot reversion point;

identify a second read-only sub-volume associated with a snapshot taken more recently than the snapshot reversion point;

remove the first writeable sub-volume associated with the volume from the distributed file system;

remove the identified second read-only sub-volume from the distributed file system; and

mark the first read-only sub-volume associated with the snapshot reversion point as writeable.

12. The system of claim 8, wherein the processing device is further to:

receive an instruction to perform a read operation on an object in the volume;

determine that the object does not exist in the first writeable sub-volume;

determine that the object exists in a read-only sub-volume; and

perform the read operation on the object in the read-only sub-volume.

13. The system of claim 8, wherein the memory and the processing device are located on a storage node of the distributed file system.

14. The system of claim 8, wherein the processing device is further to:

receive an instruction to delete a snapshot for deletion;

determine that the snapshot for deletion is a terminal snapshot;

remove the first writeable sub-volume associated with the snapshot for deletion; and

mark a read-only sub-volume associated a most recent snapshot as writeable.

15. A non-transitory machine-readable storage medium storing instructions that cause a processing device to:

initiate, by a processing device, a snapshot of a volume distributed across a plurality of storage nodes of a distributed file system;

create, by the processing device, a writeable sub-volume associated with the volume of the distributed file system; and

mark, by the processing device, the volume of the distributed file system as read-only;

receiving an instruction to perform a deletion of an object in the volume;

determining that the object exists in a read-only sub-volume associated with the volume; and

generating a negative entry for the object in the writeable sub-volume.

16. The non-transitory machine-readable storage medium of claim 15, further comprising instructions to cause the processing device to:

initiate a second snapshot of the volume of the distributed file system;

create a second writeable sub-volume associated with the volume of the distributed file system; and

mark the writeable sub-volume associated with the volume of the distributed file system as read-only.

17. The non-transitory machine-readable storage medium of claim 15, further comprising instructions to cause the processing device to:

initiate a reversion to the snapshot;

remove the writeable sub-volume from the distributed file system; and

mark the volume of the distributed file system as writeable.