Convert Lazy Zeroed Disk to Eager Zeroed Disk

We plan to build a new file server cluster by utilizing couple existing Windows 2012 R2 in the VMware 5.5 farm. According to the VMware KB, the system drive has to be created with Eager Zeroed  disk, I think the reason is to have low disk latency otherwise the high disk latency may lead to failover.

The existing boxes’ system drives are currently on the Lazy Zeroed disk, to convert it to the Eager Zeroed disk. Here is the process:

1) Power off the VM.

2) SSH into the host and run the vmkfstools -k vmname.vmdk

3) Power on the VM.

To check whether the disk is Lazy or Eager zeroed, the command is vmkfstools -D vmname-flat.vmdk, check the tbz (it means the number of blocks in the disk remaining to be zeroed). If it is not 0, then it mean it is Lazy zeroed disk.

Example:

vmkfstools -D myvm-flat.vmdk
Lock [type 10c00001 offset 219779072 v 2377, hb offset 3256320
gen 171, mode 0, owner 00000000-00000000-0000-000000000000 mtime 50509820 nHld 0 nOvf 0]
Addr <4, 494, 34>, gen 2353, links 1, type reg, flags 0, uid 0, gid 0, mode 600
len 77309411328, nb 73728 tbz 31343, cow 0, newSinceEpoch 0, zla 3, bs 1048576

vmkfstools -k myvm.vmdk
Eagerly zeroing: 100% done.

vmkfstools -D myvm-flat.vmdk
Lock [type 10c00001 offset 219779072 v 2379, hb offset 4161536
gen 83, mode 0, owner 00000000-00000000-0000-000000000000 mtime 22553695 nHld 0 nOvf 0]
Addr <4, 494, 34>, gen 2353, links 1, type reg, flags 0, uid 0, gid 0, mode 600
len 77309411328, nb 73728 tbz 0, cow 0, newSinceEpoch 0, zla 3, bs 1048576