VNX 5400 Thin pool lun consumed capacity

Hello,

When you provision storage from a VNX pool to VMware Datastores, they'll show up on Unisphere as full/used, even if no data exists on this allocated space.

From the VNX with MCx Virtual Provisioning White Paper, page 42:

For VMware environments, the Virtual Machine File System (VMFS) has many

characteristics that are thin-friendly. First, a minimal number of thin extents are

allocated from the pool when a VMware file system is created on thin LUNs. Also, a

VMFS Datastore reuses previously allocated blocks that are beneficial to thin LUNs.

When using RDM volumes, the file system or device created on the guest OS dictates

whether the RDM volume is thin-friendly.

When creating a VMware virtual disk, LUNs can be provisioned as:

 Thick Provision Lazy Zeroed

 Thick Provision Eager Zeroed

 Thin Provision

Thick Provision Lazy Zeroed is the default and recommended virtual disk type for thin

LUNs. When using this method, the storage required for the virtual disk is reserved in

the Datastore, but the VMware kernel does not initialize all the blocks at creation.

The VMware kernel also provides other mechanisms for creating virtual drives that are

not thin-friendly. The Thick Provision Eager Zeroed format is not recommended for

thin LUNs because it performs a write to every block of the virtual disk at creation.

This results in equivalent storage use in the thin pool.

When using Thin Provision, space required for the virtual disk is not allocated at

creation. Instead, it is allocated and zeroed out on demand.

As of vSphere 5, there is also the ability to perform thin LUN space reclamation at the

storage system level. VMFS 5 uses the SCSI UNMAP command to return space to the

storage pool when created on thin LUNs. SCSI UNMAP is used any time VMFS 5

deletes a file, such as Storage vMotion, delete VM, delete snapshot, etc. Earlier

versions of VMFS would only return the capacity at the file system level. vSphere 5

greatly simplifies the process by conducting space reclaim automatically.

In addition, features such as VMware DRS, Converter, VM Clones, Storage vMotion,

Cold Migration, Templates, and vMotion are thin-friendly.

For the full paper:

https://www.emc.com/collateral/white-papers/h12204-vp-for-new-vnx-series-wp.pdf

Hope this helps,

Adham