6.5.1

VMFSsparse is implemented on top of VMFS. The VMFSsparse layer
processes I/Os issued to a snapshot VM. Technically, VMFSsparse is a
redo-log that starts empty, immediately after a VM snapshot is taken. The
redo-log expands to the size of its base vmdk, when the entire vmdk is
rewritten with new data after the VM snapshotting. This redo-log is a file in
the VMFS datastore. Upon snapshot creation, the base vmdk attached to
the VM is changed to the newly created sparse vmdk.
SEsparse SEsparse is a default format for all delta disks on the VMFS6 datastores.
On VMFS5, SEsparse is used for virtual disks of the size 2 TB and larger.
SEsparse is a format similar to VMFSsparse with some enhancements.
This format is space efficient and supports the space reclamation
technique. With space reclamation, blocks that the guest OS deletes are
marked. The system sends commands to the SEsparse layer in the
hypervisor to unmap those blocks. The unmapping helps to reclaim space
allocated by SEsparse once the guest operating system has deleted that
data. For more information about space reclamation, see Storage Space
Reclamation.
Snapshot Migration
You can migrate VMs with snapshots across different datastores. The following considerations apply:
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If you migrate a VM with the VMFSsparse snapshot to VMFS6, the snapshot format changes to
SEsparse.
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When a VM with a vmdk of the size smaller than 2 TB is migrated to VMFS5, the snapshot format
changes to VMFSsparse.
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You cannot mix VMFSsparse redo-logs with SEsparse redo-logs in the same hierarchy.
Understanding Network File System Datastores
An NFS client built into ESXi uses the Network File System (NFS) protocol over TCP/IP to access a
designated NFS volume that is located on a NAS server. The ESXi host can mount the volume and use it
for its storage needs. vSphere supports versions 3 and 4.1 of the NFS protocol.
Typically, the NFS volume or directory is created by a storage administrator and is exported from the NFS
server. You do not need to format the NFS volume with a local file system, such as VMFS. Instead, you
mount the volume directly on the ESXi hosts and use it to store and boot virtual machines in the same
way that you use the VMFS datastores.
In addition to storing virtual disks on NFS datastores, you can use NFS as a central repository for ISO
images, virtual machine templates, and so on. If you use the datastore for the ISO images, you can
connect the CD-ROM device of the virtual machine to an ISO file on the datastore. You then can install a
guest operating system from the ISO file.
vSphere Storage
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