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Apr 11 2011

How to read Linked Clone Storage Provisioning metrics in vCenter

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Understanding storage resource utilisation by a virtual machine in vCenter Client is not difficult, especially when Thick Provisioning is in use. When the virtual machine is using Thick Provisioning all three metrics (Provisioned Storage, Not-Shared Storage and Used Storage) show exactly the same numbers.

When using Thin Provisioning the amount of provisioned storage is displayed, of course, in Provisioned Storage. The other two metrics will show the amount of Storage in Use. The Used Storage metric include swap files, log files, suspend files and any snapshots.

What about Not-Shared Storage?

Have you ever noticed that when using Linked Cloning with VMware View 4.5 or later the storage utilisation doesn’t follow the same logic? I am regularly asked about this and thought it would be good to share.

 

clone_vcenter1

 

The vCenter Client picture above demonstrate the following:

1 – Provisioned Storage 72.07GB – This is the total storage provisioned for the VM. It includes only files in the VM directory. The picture below demonstrate what files may be used to sum up the amount of provisioned storage (Provisioned Size column).

Despite the virtual machine been provisioned with 32GB of storage, when using Linked Cloning each VMDK created will show Provisioned Size of 32GB. By default VMs created by VMware View Composer will have two disks, being one pre and one post initial snapshot created by VMware View. This snapshot is used for Refresh operations. (find out more about the Refresh operation at my article VMware View 4.5 Linked Cloning Operations Explained)

2 – Not-Shared Storage 2.49GB – Just like the regular Thin Provisioning this is the total storage in use by the virtual machine. It includes only files in the VM directory. The picture below demonstrate the files that may be used to sum up the total amount of storage in use (Size column).

3 – Used Storage 12.11GB – This metric is different than the regular Thin Provisioning. For Linked Clones created with VMware View Composer this metric represent the total storage in use by the VM, including the Replica (Replica + VM). The metric includes used storage in the Replica Folder and in the VM folder.

It is correct to assume that Used Storage (12.11GB) – Not-Shared Storage (2.49GB) = Replica (9.62GB).

clone_vcenter

 

A Funny note is that despite Delta disks are Thin Provisioned, in vCenter their type is set as Thick (see picture below). The additional disks such as the persistent data disk and the disposable disk are shown as Thin.

delta00

 

The reason for that is the Hard disk 1 is actually a vmfsSparse disk. This disk file type consists of a virtual disk descriptor file and paired delta extent file. These data files are based on the vmfsSparse format, intended to store delta content or "change data" for a period of time, otherwise known as a snapshot. In other words, this disk points to the Replica Disk, therefore follow the Replica type. An example of a file descriptor is snippet below.

# Disk DescriptorFile
version=1
encoding="UTF-8"
CID=4097ff2b
parentCID=2eea12c2
isNativeSnapshot="no"
createType="vmfsSparse"
parentFileNameHint="/vmfs/volumes/4c872f50-edf8f84c-c5c7-000c29471840/replica-89ad13bd-cbd1-4f6d-b40f-/replica-89ad13bd-cbd1-4f6d-b40f-.vmdk"
# Extent description
RW 50331648 VMFSSPARSE "VMView-F-01-delta.vmdk"

# The Disk Data Base
#DDB

ddb.longContentID = "a0d0a233131c9e567150282a4097ff2b"

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Permanent link to this article: http://myvirtualcloud.net/?p=1853

2 pings

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