This article may be helpful when you encounter these issues:
When creating a snapshot, there are several options you can specify:
flag is 1 or true, a dump of the internal state of the virtual machine is included in the snapshot. Memory snapshots take longer to create.
flag is 1 or true, and the virtual machine is powered on when the snapshot is taken, VMware Tools is used to quiesce the file system in the virtual machine. Quiescing a file system is a process of bringing the on-disk data of a physical or virtual computer into a state suitable for backups. This process might include such operations as flushing dirty buffers from the operating system's in-memory cache to disk, or other higher-level application-specific tasks.
When a snapshot is created, it is comprised of these files:
- .vmdk - -delta.vmdk
-delta.vmdkfiles for each virtual disk is connected to the virtual machine at the time of the snapshot. These files can be referred to as child disks, redo logs, or delta links. These child disks can later be considered parent disks for future child disks. From the original parent disk, each child constitutes a redo log pointing back from the present state of the virtual disk, one step at a time, to the original.
value may not be consistent across all child disks from the same snapshot. The file names are chosen based on filename availability.
.vmsdfile is a database of the virtual machine's snapshot information and the primary source of information for the snapshot manager. The file contains line entries which define the relationships between snapshots as well as the child disks for each snapshot.
These files are the memory state at the time of the snapshot.
In addition to being able to use snapshot manager to create snapshots, snapshots are used by many VMware and third-party products and features. Some VMware products that use snapshots extensively are:
Note: This is not an exhaustive list.
Our VMware API allows VMware and third-party products to perform operations with virtual machines and their snapshots. This is a list of common operations that can be performed on virtual machines and snapshots using our API:
This is a high-level overview of how to create, remove, or revert snapshot requests that are processed within the VMware environment:
.vmsdfile) and the changes are reflected in the snapshot manager of the virtual machine.
.vmdkfiles) and the disk chain.
The child disk, which is created with a snapshot, is a sparse disk. Sparse disks employ the copy-on-write (COW) mechanism, in which the virtual disk contains no data in places, until copied there by a write. This optimization saves storage space. The grain is the unit of measure in which the sparse disk uses the copy-on-write mechanism. Each grain is a block of sectors containing virtual disk data. The default size is 128 sectors or 64KB.
It is important to note these points regarding the space utilization of child disks:
These Knowledge Base articles touch on the topic of child disks and disk usage:
Generally, when you create a snapshot for the first time, the first child disk is created from the parent disk. Successive snapshots generate new child disks from the last child disk on the chain. The relationship can change if you have multiple branches in the snapshot chain.
This diagram is an example of a snapshot chain. Each square represents a block of data or a grain as described above:
Caution: Manually manipulating the individual child disks or any of the snapshot configuration files may compromise the disk chain. VMware does not recommend manually modifying the disk chain as it may result in data loss. For more information, seeConsolidating snapshots (1007849).