6.5.1

The files that make up the delta disk are called child disks or redo logs.
Flat file A -flat.vmdk file that is one of two files that comprises the base disk. The
flat disk contains the raw data for the base disk. This file does not appear
as a separate file in the Datastore Browser.
Database file A .vmsd file that contains the virtual machine's snapshot information and is
the primary source of information for the Snapshot Manager. This file
contains line entries, which define the relationships between snapshots and
between child disks for each snapshot.
Memory file A .vmsn file that includes the active state of the virtual machine. Capturing
the memory state of the virtual machine lets you revert to a turned on virtual
machine state. With nonmemory snapshots, you can only revert to a turned
off virtual machine state. Memory snapshots take longer to create than
nonmemory snapshots. The time the ESXi host takes to write the memory
onto the disk depends on the amount of memory the virtual machine is
configured to use.
A Take Snapshot operation creates .vmdk, -delta.vmdk, vmsd, and vmsn files.
File Description
vmname-number.vmdk and vmname-
number-delta.vmdk
Snapshot file that represents the difference between the current state of the virtual disk and
the state that existed at the time the previous snapshot was taken.
The filename uses the following syntax, S1vm-000001.vmdk where S1vm is the name of the
virtual machine and the six-digit number, 000001, is based on the files that already exist in
the directory. The number does not consider the number of disks that are attached to the
virtual machine.
vmname.vmsd
Database of the virtual machine's snapshot information and the primary source of
information for the Snapshot Manager.
vmname.Snapshotnumber.vmsn
Memory state of the virtual machine at the time you take the snapshot. The filename uses
the following syntax, S1vm.snapshot1.vmsn, where S1vm is the virtual machine name, and
snapshot1 is the first snapshot.
Note A .vmsn file is created each time you take a snapshot, regardless of the memory
selection. A .vmsn file without memory is much smaller than one with memory.
Snapshot Limitations
Snapshots can affect virtual machine performance and do not support some disk types or virtual
machines configured with bus sharing. Snapshots are useful as short-term solutions for capturing point-
in-time virtual machine states and are not appropriate for long-term virtual machine backups.
n
VMware does not support snapshots of raw disks, RDM physical mode disks, or guest operating
systems that use an iSCSI initiator in the guest.
n
Virtual machines with independent disks must be powered off before you take a snapshot. Snapshots
of powered-on or suspended virtual machines with independent disks are not supported.
vSphere Virtual Machine Administration
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