SYSTEM SOFTWARE INTERFACES FOR SPACE-OPTIMIZED BLOCK DEVICES

• US 20120054746A1
• Filed: 07/12/2011
• Published: 03/01/2012
• Est. Priority Date: 08/30/2010
• Status: Active Grant

• Current Assignee: Vmware LLC (Broadcom, Inc.)
• Original Assignee: VMware, Inc. (Broadcom, Inc.)
• Inventors: VAGHANI, Satyam B., ASWATHANARAYANA, Tejasvi
• Granted Patent: US 9,411,517 B2
• Time in Patent Office: Days
• US Class Current: 718/1
• CPC Class Codes: G06F 12/0253 Garbage collection, i.e. reclamation of unreferenced memory
• CPC Class Codes: G06F 2009/4557 Distribution of virtual machine instances; Migration and load balancing
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0664 at device level, e.g. emulation of a storage device or system
• CPC Class Codes: G06F 3/0665 at area level, e.g. provisioning of virtual or logical volumes
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects
• CPC Class Codes: G06F 9/4856 resumption being on a different machine, e.g. task migration, virtual machine migration G06F9/5088 takes precedence
• CPC Class Codes: G06F 9/5022 Mechanisms to release resources

Abstract

Interfaces to storage devices that employ storage space optimization technologies, such as thin provisioning, are configured to enable the benefits gained from such technologies to be sustained. Such an interface may be provided in a hypervisor of a virtualized computer system to enable the hypervisor to discover features of a logical unit number (LUN), such as whether or not the LUN is thinly provisioned, and also in a virtual machine (VM) of the virtualized computer system to enable the VM to discover features of a virtual disk, such as whether or not the virtual disk is thinly provisioned. The discovery of these features enables the hypervisor or the VM to instruct the underlying storage device to carry out certain operations such as an operation to deallocate blocks previously allocated to a logical block device, so that the storage device can continue to benefit from storage space optimization technologies implemented therein.

Claims

1. A method of issuing a command to deallocate free storage blocks previously allocated to a logical block device, comprising:

determining that the logical block device supports the command;

identifying one or more sets of contiguous storage blocks to be deallocated; and

issuing the command to the logical block device based on alignment and granularity values according to which the logical block device performs space reclamation operations, the command identifying at least one set of contiguous storage blocks as storage blocks to be deallocated.

2. The method of claim 1, further comprising:

determining that a set of contiguous storage blocks is not compatible with the alignment and granularity values; and

identifying the set of contiguous storage blocks in a data structure.

3. The method of claim 2, further comprising:

coalescing two or more sets of contiguous storage blocks that are identified in the data structure; and

issuing another command to the logical block device based on the alignment and granularity values, said another command identifying the coalesced sets of contiguous storage blocks as storage blocks to be deallocated.

4. The method of claim 2, further comprising:

detecting a write operation on a storage block identified in the data structure; and

removing the storage block from the data structure.

5. The method of claim 1, wherein the logical block device is a logical unit number (LUN) to which a hypervisor of a virtualized computer system is interfaced.

6. The method of claim 5, wherein the hypervisor supports execution of one or more virtual machines and receives from a virtual machine a request to deallocate guest storage blocks from a virtual disk for the virtual machine.

7. The method of claim 6, further comprising:

identifying storage blocks of the LUN corresponding to the guest storage blocks to be deallocated.

8. The method of claim 7, wherein the identified storage blocks of the LUN correspond to the one or more sets of contiguous storage blocks to be deallocated.

9. The method of claim 7, wherein the identified storage blocks of the LUN are indicated as to be zeroed.

10. The method of claim 7, wherein the identified storage blocks of the LUN are indicated as free in a bitmap of storage blocks of the LUN maintained by the hypervisor.

11. The method of claim 5, further comprising:

performing live migration of virtual machine files stored in the LUN to another LUN,

wherein the virtual machine files are stored in the one or more sets of contiguous storage blocks to be deallocated.

12. The method of claim 1, wherein the logical block device is a virtual disk for a virtual machine, and the virtual disk is represented as at least one file in a logical unit number (LUN).

13. A non-transitory computer readable storage medium comprising instructions executable by a computer system to carry out a method of issuing a command to deallocate free storage blocks previously allocated to a logical block device, said method comprising:

determining that the logical block device supports the command;

identifying one or more sets of contiguous storage blocks to be deallocated; and

issuing the command to the logical block device based on alignment and granularity values according to which the logical block device performs space reclamation operations, the command identifying at least one set of contiguous storage blocks as storage blocks to be deallocated.

14. The non-transitory computer readable storage medium of claim 13, wherein the method further comprises:

determining that a set of contiguous storage blocks is not compatible with the alignment and granularity values; and

identifying the set of contiguous storage blocks in a data structure.

15. The non-transitory computer readable storage medium of claim 14, wherein the method further comprises:

coalescing two or more sets of contiguous storage blocks that are identified in the data structure; and

issuing another command to the logical block device based on the alignment and granularity values, said another command identifying the coalesced sets of contiguous storage blocks as storage blocks to be deallocated.

17. A computer system comprising:

hardware resources including a processor, memory, and a logical block device; and

a hypervisor that supports execution of one or more virtual machines and emulates the hardware resources for the virtual machines including an emulated logical block device,

wherein the hypervisor includes a component for issuing commands to the logical block device to deallocate storage blocks from the logical block device, and the virtual machines each include a component for issuing commands to the emulated logical block device to deallocate storage blocks from the emulated logical block device.

18. The computer system of claim 17, wherein the commands to the logical block device are issued based on alignment and granularity values according to which the logical block device performs space reclamation operations, and the commands to the emulated logical block device are issued based on alignment and granularity values according to which the emulated logical block device performs space reclamation operations.

19. The computer system of claim 18, wherein the hypervisor manages a first data structure in which storage blocks that are to be deallocated but not compatible with the alignment and granularity values of the logical block device are identified, and the virtual machines each manage a second data structure in which storage blocks that are to be deallocated but not compatible with the alignment and granularity values of the emulated logical block device are identified.

20. The computer system of claim 19, wherein the hypervisor removes from the first data structure a storage block if the hypervisor detects a write to the storage block, and the virtual machines each remove from the second data structure a storage block if the virtual machine detects a write to the storage block.

21. A method for issuing a command to deallocate free storage blocks previously allocated to a logical block device, comprising:

identifying a set of free blocks to be released from a data structure maintained by a hypervisor of a virtualized computer system;

allocating the free blocks in the set to a file and marking the free blocks allocated to the file as used in the data structure; and

issuing a command to the logical block device to deallocate the free blocks allocated to the file.

22. The method of claim 21, further comprising:

marking the free blocks allocated to the file as free in the data structure.

23. The method of claim 21, wherein the number of free blocks in the set represents a portion of all free blocks.

24. The method of claim 22, wherein the portion represents a percentage of all free blocks that is empirically determined.

25. The method of claim 21, further comprising:

upgrading a computer system coupled to the logical block device,

wherein the steps of identifying, allocating, and issuing are carried out after the step of upgrading.

26. The method of claim 25, wherein the computer system includes a hypervisor that supports execution of one or more virtual machines, and the computer system is upgraded from a hypervisor that does not support thin provisioning to a hypervisor that supports thin provisioning.

27. The method of claim 26, wherein the steps of identifying, allocating, and issuing are invoked periodically by a space monitoring process running in the computer system.

28. The method of claim 26, wherein the steps of identifying, allocating, and issuing are carried out in response to a command from a server that manages the virtual machines.

29. The method of claim 26, wherein the steps of identifying, allocating, and issuing are carried out in response to a manual user input.