In persistent disk mode, changes are immediately and permanently written to the virtual disk, so that they survive even through to the next power on.
In nonpersistent mode, changes to the virtual disk are discarded when the virtual machine powers off. The VMDK files revert to their original state.
VMDK Virtual Disk Files explains the different types of virtual disk. The first column corresponds to
Virtual Disk Types but without the
VIXDISKLIB_DISK prefix. The third column gives the possible names of VMDK files as implemented on Workstation and ESX/ESXi hosts.
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In Select A Disk Type, accepting the defaults by not checking any box produces one VMDK file that can grow larger if more space is needed. The <vmname> represents the name of a virtual machine.
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If you select only the Allocate all disk space now check box, space is pre-allocated, so the virtual disk cannot grow. The first VMDK file is small and points to a much larger one, whose filename says flat without a sequence number.
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If you select only the Split disk into 2GB files check box, virtual disk can grow when more space is needed. The first VMDK file is small and points to a sequence of other VMDK files, all of which have an s before a sequence number, meaning sparse. The number of VMDK files depends on the disk size requested. As data grows, more VMDK files are added in sequence.
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If you select the Allocate all disk space now and Split disk into 2GB files check boxes, space is pre-allocated, so the virtual disk cannot grow. The first VMDK file is small and points to a sequence of other files, all of which have an f before the sequence number, meaning flat. The number of files depends on the requested size.
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A redo log (or child disk or delta link) is created when a snapshot is taken of a virtual machine, or with the virtual disk library. Snapshot file numbers are in sequence, without an s or f prefix. The numbered VMDK file stores changes made to the virtual disk <diskname> since the original parent disk, or previously numbered redo log (in other words the previous snapshot).
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Provisioned size for a thin disk is the maximum size the disk will occupy when fully allocated. Actual size is the current size of the thin disk. Overcommit means that if all thin disks were fully provisioned, there would not be enough space to accommodate all of the thin disks.
The path name to a virtual machine and its VMDK can be expressed with any character set supported by the host file system. As of vSphere 4 and Workstation 7, VMware supports Unicode UTF-8 path names, although for portability to various locales, ASCII-only path names are recommended.
Windows 2000 systems (and later) use UTF-16 for localized path names. For example, in locale FR (Français) the VDDK sample code might mount disk at C:\Windows\Temp\vmware-Système, where è is encoded as UTF-16 so the VixMntapi library cannot recognize it. In this case, a workaround is to set the
tmpDirectory configuration key with an ASCII-only path before program start-up; see
Initialize the Library.
For programs opening arbitrary path names, Unicode offers a GNU library with C functions iconv_open() to initialize codeset conversion, and
iconv() to convert UTF-8 to UTF-16, or UTF-16 to UTF-8.
Click the Request... specification link. Provide your name, organization, and email address. A link to the online PDF document should arrive shortly in your email inbox. The
Virtual Disk Format 5.0 technical note provides useful information about the VMDK format.
SPARSE type virtual disks use a hierarchical representation to organize sectors. See
Virtual Disk Format 5.0 referenced in
Virtual Disk Internal Format. In this context, grain means granular unit of data, larger than a sector. The hierarchy includes: