VIRTUALIZATION OF NON-VOLATILE RANDOM ACCESS MEMORY

• US 20170123685A1
• Filed: 11/04/2015
• Published: 05/04/2017
• Est. Priority Date: 11/04/2015
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Nimble Storage (Hewlett-Packard Enterprise Company)
• Inventors: Barszczak, Tomasz, Zuo, Xiaoshan
• Granted Patent: US 10,019,193 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G06F 3/0673 Single storage device

Abstract

Methods, systems, and computer programs are presented for virtualizing Non-Volatile Random Access Memory (NVRAM). A first area in RAM is labeled as active area and a second area as non-active area, and an active journal and a non-active journal are created in permanent storage. A transaction is created for each write made to the virtual NVRAM, and the created transactions are written to the active journal and to the active area. When the active journal is greater than a predetermined size or a timeout occurs, a checkpoint is created by copying contents from the active area to the non-active area, switching status of the active area and the non-active areas (the active area becomes the non-active area and the non-active area becomes the active area), switching status of the active journal and the non-active journal, and copying the content of the current non-active area to permanent storage.

Claims

1. A method for virtualizing Non-Volatile Random Access Memory (NVRAM), the method comprising:

labeling a first area in Random Access Memory (RAM) as active area and a second area in RAM as non-active area;

creating, in permanent storage, an active journal and a non-active journal;

creating a transaction for each write made to the virtual NVRAM;

writing the created transactions to the active journal and to the active area; and

when the active journal is substantially full, creating a checkpoint, wherein creating the checkpoint includes;

copying contents from the active area to the non-active area;

switching status of the active area and the non-active areas, wherein the active area becomes the non-active area and the non-active area becomes the active area;

switching status of the active journal and the non-active journal; and

copying contents of the current non-active area to permanent storage.

2. The method as recited in claim 1, wherein writing the transactions to the active journal and to the active area includes:

storing a plurality of transactions into a record;

writing the record into the active journal kept; and

updating contents of the active area based on the record written to the active journal.

3. The method as recited in claim 1, wherein creating the checkpoint further includes:

before copying contents from the active area, blocking new writes to the NVRAM; and

after switching status of the active journal and the non-active journal, unblocking the new writes to the NVRAM; and

terminating the current non-active journal.

4. The method as recited in claim 1, wherein switching status of the active journal and the non-active journal further includes:

initializing the current active journal.

5. The method as recited in claim 1, wherein a first superblock in permanent storage keeps information on the active journal.

6. The method as recited in claim 5, further including:

after a warm recovery of a system hosting the virtual NVRAM,

reading the first superblock to identify active area and non-active area;

writing the active area to a non-active checkpoint on permanent storage; and

switching active and non-active checkpoints on permanent storage.

7. The method as recited in claim 5, further including:

after a cold recovery of a system hosting the virtual NVRAM,

reading the first superblock to identify active area and non-active area;

loading a valid checkpoint into active area;

replaying records on the active journal to be loaded into the active area; and

saving non-active area to a non-active checkpoint on permanent storage.

8. A system for virtualizing Non-Volatile Random Access Memory (NVRAM), the system comprising:

a processor;

a Random Access Memory (RAM), wherein the processor labels a first area in RAM as active area and a second area in RAM as non-active area; and

permanent storage storing an active journal and a non-active journal, wherein the processor creates a transaction for each write made to the virtual NVRAM and the processor writes the created transactions to the active journal and to the active area;

wherein when the active journal is substantially full, the processor creates a checkpoint in the permanent storage, wherein creating a checkpoint includes;

copying contents from the active area to the non-active area;

switching status of the active area and the non-active areas, wherein the active area becomes the non-active area and the non-active area becomes the active area;

switching status of the active journal and the non-active journal; and

copying contents of the current non-active area to permanent storage.

9. The system as recited in claim 8, wherein when writing the transactions to the active journal and to the active area, the processor stores a plurality of transactions into a record, writes the record into the active journal kept, and updates contents of the active area based on the record written to the active journal.

10. The system as recited in claim 8, wherein when creating the checkpoint the processor, before copying contents from the active area, blocks new writes to the NVRAM, wherein after switching status of the active journal and the non-active journal, the processor unblocks the new writes to the NVRAM;

and terminating the current non-active journal.

11. The system as recited in claim 8, wherein when switching status of the active journal and the non-active journal the processor initializes the current active journal.

12. The system as recited in claim 8, wherein a first superblock in permanent storage keeps information on the active journal.

13. The system as recited in claim 12, wherein after a warm recovery of a system hosting the virtual NVRAM, the processor reads the first superblock to identify active area and non-active area, the processor writes the active area to a non-active checkpoint on permanent storage, and the processor switches active and non-active checkpoints on permanent storage.

14. The system as recited in claim 12, wherein after a cold recovery of a system hosting the virtual NVRAM, the processor reads the first superblock to identify active area and non-active area, the processor loads a valid checkpoint into active area, the processor replays records on the active journal to be loaded into the active area, and the processor saves non-active area to a non-active checkpoint on permanent storage.

15. A non-transitory computer-readable storage medium storing a computer program for virtualizing Non-Volatile Random Access Memory (NVRAM), the computer-readable storage medium comprising:

program instructions for labeling a first area in Random Access Memory (RAM) as active area and a second area in RAM as non-active area;

program instructions for creating, in permanent storage, an active journal and a non-active journal;

program instructions for creating a transaction for each write made to the virtual NVRAM;

program instructions for writing the created transactions to the active journal and to the active area; and

program instructions for when the active journal is greater than a predetermined size or a timeout occurs, creating a checkpoint, wherein creating a checkpoint includes;

copying contents from the active area to the non-active area;

switching status of the active area and the non-active areas, wherein the active area becomes the non-active area and the non-active area becomes the active area;

switching status of the active journal and the non-active journal; and

copying contents of the current non-active area to permanent storage.

16. The storage medium as recited in claim 15, wherein writing the transactions to the active journal and to the active area includes:

program instructions for storing a plurality of transactions into a record;

program instructions for writing the record into the active journal kept; and

program instructions for updating contents of the active area based on the record written to the active journal.

17. The storage medium as recited in claim 15, wherein creating the checkpoint further includes:

program instructions for before copying contents from the active area, blocking new writes to the NVRAM; and

program instructions for after switching status of the active journal and the non-active journal, unblocking the new writes to the NVRAM; and

terminating the current non-active journal.

18. The storage medium as recited in claim 15, wherein switching status of the active journal and the non-active journal further includes:

program instructions for initializing the current active journal.

19. The storage medium as recited in claim 15, wherein a first superblock in permanent storage keeps information on the active journal.

20. The storage medium as recited in claim 19, further including:

program instructions for, after a warm recovery of a system hosting the virtual NVRAM,

reading the first superblock to identify active area and non-active area;

writing the active area to a non-active checkpoint on permanent storage; and

switching active and non-active checkpoints on permanent storage.