厚置备延迟置零：以默认的厚格式创建虚拟磁盘。创建过程中为虚拟磁盘分配所需空间。创建时不会擦除物理设备上保留的任何数据，但是以后从虚拟机首次执行写操作时会按需要将其置零。

厚置备置零：创建支持群集功能（如 Fault Tolerance）的厚磁盘。在创建时为虚拟磁盘分配所需的空间。与平面格式相反，在创建过程中会将物理设备上保留的数据置零。创建这种格式的磁盘所需的时间可能会比创建其他类型的磁盘长。

精简置备：使用精简置备格式。最初，精简置备的磁盘只使用该磁盘最初所需要的数据存储空间。如果以后精简磁盘需要更多空间，则它可以增长到为其分配的最大容量

名词出现场景

VMware中，使用vSphere Client创建新的虚拟机时（无上面英文提到情况不会出现下列选项），在配置指定置备策略时有三个选项：
厚置备延迟置零（zeroed thick）
厚置备置零（eager zeroed thick）
精简置备（thin）

四个名词解释（一）：

zeroedthick (default) .

Space required for the virtual disk is allocated during creation. Any data remaining on the physical device is not erased during creation, but will be zeroed out at a later time during virtual machine read and write operations.

eagerzeroedthick

Space required for the virtual disk is allocated at creation time. Unlike with the zeroedthick format, the data remaining on the physical device is zeroed out during creation. Disks in this format might take much longer to create than other types of disks.

thick

Space required for the virtual disk is allocated during creation. This type of formatting doesn.t zero out any old data that might be present on this allocated space.

thin

Thin-provisioned virtual disk. Unlike with the thick format, space required for the virtual disk is not allocated during creation, but is supplied, zeroed out, on demand at a later time.

You only need thin when exporting VMDKs from ESX, since many OS / tools have problems accessing files larger 2GB

四个名词解释（二）：

zeroedthink

the disk is allocated at creation and all space wiped (not necessarily at creation time)

eagerzeroedthick

the disk is allocated and all space zeroed at creation time

thick

same as zeroedthick without wiping the data

thin

same as thick but split into 2gb chunks

四个名词解释（三）：

zeroedthick

when the VM reads sectors itself hasn't already written to it gets wiped (random) data

eagerzeroedthick

when the VM reads sectors itself hasn't already written to it gets zeroed (all bytes set to zero) data, in this case the overwriting with zeroes takes place when the vmdk is created

thick

when the VM reads sectors itself hasn't already written to it gets the data that was stored on the physical disk before (possible security risk - depending on the environment and regulatories)

thin

the same as thick (thin is normally only used for exporting vmdks)

四个名词解释（四）：

`zeroedthick`

This is the default option when creating new virtual disks.

A zeroed thick disk has all space allocated at creation time, and this space is wiped clean of any previous contents on the physical media.

`eagerzeroedthick`

An eager zeroed thick disk has all space allocated and zeroed out at creation time. Such disks may take longer time during creation compared to other disk formats.

`thick`

A thick disk has all space allocated at creation time. This space may contain stale data as it exists on the physical media.

`thin`

Space required for thin-provisioned virtual disk is allocated and zeroed on demand as opposed to upon creation.

zeroedthick与eagerzeroedthick比较

In some cases while working in your VMware environment it’s very important to know what type of virtual disk you’re working with. A few of these functions are Fault Tolerance and Microsoft Clustered Services.

You can easily determine the type of disk using vmkfstools -t0, for example:

The following is an example of a zeroedthick disk

# vmkfstools -t0 /vmfs/volumes/datastore1/EagerBeaver/EagerBeaver.vmdk | more
Mapping for file /vmfs/volumes/4aef08e3-671b60d5-927b-00188be583a5/EagerBeaver/EagerBeaver.vmdk (8589934592 bytes in size):
[ 0: 196083712] --> [VMFSZ- LVID:4aef08e2-0e1d23e2-2505-00188be583a5/4aef08e2-046dd3fa-28b3-00188be583a5/1:( 275392790016 --> 275588873728)]
[ 196083712: 12582912] --> [VMFSZ- LVID:4aef08e2-0e1d23e2-2505-00188be583a5/4aef08e2-046dd3fa-28b3-00188be583a5/1:( 275379158528 --> 275391741440)]
[ 208666624: 8381267968] --> [VMFSZ- LVID:4aef08e2-0e1d23e2-2505-00188be583a5/4aef08e2-046dd3fa-28b3-00188be583a5/1:( 275588873728 --> 283970141696)]
Note: Notice in the zerothicked VM’s you have a Z following VMFS. This indicates that the block has been zeroed, but not written.

Now is an example of an eagerzeroedthick disk

# vmkfstools -t0 /vmfs/volumes/datastore1/EagerBeaver/EagerBeaver_1.vmdk | more
Mapping for file /vmfs/volumes/4aef08e3-671b60d5-927b-00188be583a5/EagerBeaver/EagerBeaver_1.vmdk (8589934592 bytes in size):
[ 0: 7516192768] --> [VMFS -- LVID:4aef08e2-0e1d23e2-2505-00188be583a5/4aef08e2-046dd3fa-28b3-00188be583a5/1:( 283970141696 --> 291486334464)]
[ 7516192768: 460324864] --> [VMFS -- LVID:4aef08e2-0e1d23e2-2505-00188be583a5/4aef08e2-046dd3fa-28b3-00188be583a5/1:( 5015371264 --> 5475696128)]
[ 7976517632: 613416960] --> [VMFS -- LVID:4aef08e2-0e1d23e2-2505-00188be583a5/4aef08e2-046dd3fa-28b3-00188be583a5/1:( 291486334464 --> 292099751424)]
You’ll notice that following the VMFS you have --, which indicates that it has the bit been completely zeroed.

Zeroedthick is a quick format and eagerzeroedthick is a full format ！