Abstract: One or more embodiments provide techniques for accessing a memory page of a virtual machine for which loading might have been deferred, according to an embodiment of the invention, includes the steps of examining metadata of the memory page and determining that a flag in the metadata for indicating that the contents of the memory page needs to be updated is set, and updating the contents of the memory page.

Abstract: A method for opening a virtual disk comprises reading information from a metadata file that identifies the current owner of the virtual disk. The method further includes sending a release request to the current owner of the virtual disk to release the virtual disk, writing information to the metadata file identifying the new owner, and then opening the virtual disk.

Abstract: Updating contents of certain memory pages in a virtual machine system is deferred until they are needed. Specifically, certain page update operations are deferred until the page is accessed for a load or store operation. Each page within the virtual machine system includes associated metadata, which includes a page signature characterizing the contents of a corresponding page or a reference to a page with canonical contents, and a flag that indicates the page needs to be updated before being accessed. The metadata may also include a flag to indicate that a backing store of the memory page has contents of a known content class. When such a memory page is mapped to a shared page with contents of that known content class, a flag in the metadata to indicate that contents of the memory page needs to be updated is not set.

Abstract: When a request is made to retrieve a guest physical page from memory and a page fault occurs, a guest virtual page address that corresponds to the guest physical page is identified along with addresses for guest virtual pages that are near the guest virtual page in the virtual address space. Each identified guest virtual page address is translated into a corresponding guest physical page address and the corresponding guest physical pages are loaded into memory.

Abstract: A method for opening a virtual disk comprises reading information from a metadata file that identifies the current owner of the virtual disk. The method further includes sending a release request to the current owner of the virtual disk to release the virtual disk, writing information to the metadata file identifying the new owner, and then opening the virtual disk.

Abstract: Methods and apparatus for saving and/or restoring state information for virtualized computing systems are described. An example apparatus includes a physical memory and a virtual machine monitor to: in response to a request to suspend operation of a virtual machine, place a trace on a memory page in the physical memory to detect at least one of a read access or a write access that occurs when state information of the virtual machine is saved in response to the request, the memory page associated with virtual memory hosted by the virtual machine, while the virtual machine continues to operate after the request, initiate storing of the virtual memory of the virtual machine, and in response to a trigger of the trace, store an indication that the memory page is an active memory page.

Abstract: To create a backup of a live (running) virtual machine, a backup agent may take a snapshot of the virtual machine, backup the virtual machine from the snapshot disk, and delete the snapshot. Deleting the snapshot initiates a snapshot consolidation process where delta disks of the virtual machine are collapsed. A virtual disk layer sets up a mirror driver between a current virtual disk and a target virtual disk. Data sectors of the delta disk are copied over to the target virtual disk in a single pass, while the mirror driver mirrors write request for the current virtual disk to the target virtual disk.

Abstract: When a request is made to retrieve a guest physical page from memory and a page fault occurs, a guest virtual page address that corresponds to the guest physical page is identified along with addresses for guest virtual pages that are near the guest virtual page in the virtual address space. Each identified guest virtual page address is translated into a corresponding guest physical page address and the corresponding guest physical pages are loaded into memory.

Abstract: Page data of a virtual machine is represented for efficient save and restore operations. One form of representation applies to each page with an easily identifiable pattern. The page is described, saved, and restored in terms of metadata reflective of the pattern rather than a complete page of data reflecting the pattern. During a save or restore operation, however, the metadata of the page is represented, but not the page data. Another form of representation applies to each page sharing a canonical instance of a complex pattern that is instantiated in memory during execution, and explicitly saved and restored. Each page sharing the canonical page is saved and restored as a metadata reference, without the need to actually save redundant copies of the page data.

Abstract: A framework for converting between copy-on-write (COW) and redo-based technologies is disclosed. To take a virtual disk snapshot, disk descriptor files, which include metadata information about data stored in virtual volumes (vvols), are “swizzled” such that the descriptor file for a latest redo log, to which IOs are currently performed, points to the base vvol of a COW-based vvol hierarchy. A disk descriptor file previously associated with the base vvol may also be updated to point to the vvol newly created by the snapshot operation. To revert to an earlier disk state, a snapshot may be taken before copying contents of a snapshot vvol of the COW-based vvol hierarchy to a base vvol of the hierarchy, thereby ensuring that the reversion can be rolled back if it is unsuccessful. Reference counting is performed to ensure that vvols in the vvol hierarchy are not orphaned in delete and revert use cases.

Abstract: When a request is made to retrieve a guest physical page from memory and a page fault occurs, a guest virtual page address that corresponds to the guest physical page is identified along with addresses for guest virtual pages that are near the guest virtual page in the virtual address space. Each identified guest virtual page address is translated into a corresponding guest physical page address and the corresponding guest physical pages are loaded into memory.

Abstract: A process for lazy checkpointing is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for restoring a state of a virtual machine (VM) running in a physical machine from a checkpoint file that is maintained in persistent storage includes the steps of detecting access to a memory page of the virtual machine that has not been read into physical memory of the VM from the checkpoint file, determining a storage block of the checkpoint file to which the accessed memory page maps, writing contents of the storage block in a buffer, and copying contents of a block of memory pages that includes the accessed memory page from the buffer to corresponding locations of the memory pages in the physical memory of the VM. The storage block of the checkpoint file may be compressed or uncompressed.

Abstract: A process for lazy checkpointing a virtual machine is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for saving a state of a virtual machine running in a physical machine to a checkpoint file maintained in persistent storage includes the steps of copying contents of a block of memory pages, which may be compressed, into a staging buffer, determining after the copying if the buffer is full, and upon determining that the buffer is full, saving the buffer contents in a storage block of the checkpoint file.

Abstract: A framework for converting between copy-on-write (COW) and redo-based technologies is disclosed. To take a virtual disk snapshot, disk descriptor files, which include metadata information about data stored in virtual volumes (vvols), are “swizzled” such that the descriptor file for a latest redo log, to which IOs are currently performed, points to the base vvol of a COW-based vvol hierarchy. A disk descriptor file previously associated with the base vvol may also be updated to point to the vvol newly created by the snapshot operation. To revert to an earlier disk state, a snapshot may be taken before copying contents of a snapshot vvol of the COW-based vvol hierarchy to a base vvol of the hierarchy, thereby ensuring that the reversion can be rolled back if it is unsuccessful. Reference counting is performed to ensure that vvols in the vvol hierarchy are not orphaned in delete and revert use cases.

Abstract: A process for lazy checkpointing is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for restoring a state of a virtual machine (VM) running in a physical machine from a checkpoint file that is maintained in persistent storage includes the steps of detecting access to a memory page of the virtual machine that has not been read into physical memory of the VM from the checkpoint file, determining a storage block of the checkpoint file to which the accessed memory page maps, writing contents of the storage block in a buffer, and copying contents of a block of memory pages that includes the accessed memory page from the buffer to corresponding locations of the memory pages in the physical memory of the VM. The storage block of the checkpoint file may be compressed or uncompressed.

Abstract: A process for lazy checkpointing a virtual machine is enhanced to reduce the number of read/write accesses to the checkpoint file and thereby speed up the checkpointing process. The process for saving a state of a virtual machine running in a physical machine to a checkpoint file maintained in persistent storage includes the steps of copying contents of a block of memory pages, which may be compressed, into a staging buffer, determining after the copying if the buffer is full, and upon determining that the buffer is full, saving the buffer contents in a storage block of the checkpoint file.

Abstract: Updating contents of certain memory pages in a virtual machine system is deferred until they are needed. Specifically, certain page update operations are deferred until the page is accessed for a load or store operation. Each page within the virtual machine system includes associated metadata, which includes a page signature characterizing the contents of a corresponding page or a reference to a page with canonical contents, and a flag that indicates the page needs to be updated before being accessed. The metadata may also include a flag to indicate that a backing store of the memory page has contents of a known content class. When such a memory page is mapped to a shared page with contents of that known content class, a flag in the metadata to indicate that contents of the memory page needs to be updated is not set.

Abstract: Page data of a virtual machine is represented for efficient save and restore operations. One form of representation applies to each page with an easily identifiable pattern. The page is described, saved, and restored in terms of metadata reflective of the pattern rather than a complete page of data reflecting the pattern. During a save or restore operation, however, the metadata of the page is represented, but not the page data. Another form of representation applies to each page sharing a canonical instance of a complex pattern that is instantiated in memory during execution, and explicitly saved and restored. Each page sharing the canonical page is saved and restored as a metadata reference, without the need to actually save redundant copies of the page data.

Abstract: Prior to or while the state of a virtual machine (“VM”) is being saved, such as in connection with the suspension or checkpointing of a VM, a set of one or more “active” memory pages is identified, this set of active memory pages comprising memory pages that are in use within the VM before operation of the VM is suspended. This set of active memory pages may constitute a “working set” of memory pages. To restore the state of the VM and resume operation, in some embodiments, (a) access to persistent storage is restored to the VM, device state for the VM is restored, and one or more of the set of active memory pages are loaded into physical memory; (b) operation of the VM is resumed; and (c) additional memory pages from the saved state of the VM are loaded into memory after operation of the VM has resumed.