supermanDan
Contributor
Contributor

Help understanding reclamation for thin provisioning

Hi,

Can some confirm or correct me on my understanding of potential areas that require disk reclamation in a vsphere environment?  Also have a few questions.  As far as I know, reclamation can happen at 2 levels:

1. at the guest OS level when thin provisioned vmdk's are used

2. at the esxi hypervisor level when the LUNs on the SAN are thin provisioned

Further clarification For #1....This becomes necessary when space is allocated within the vm and then deleted withing the vm.  To reclaim this, it is required to have vm-hw version 11, EnableBlockDelete=1 on hosts, esxi 6, thin provisioned vmdks, and guest OS that is capable of recognizing thin disks.  But what guest OS's are capable?  I've read some articles saying that windows 2008+ are capable; others that only windows 2012 R2+.  What about Linux?  Lastly, is it required for esxi 6.0 to have CBT disabled?  What about 6.5?

Further clarification on #2....This becomes necessary when a vm is storage vmotioned from one datastore to another or when snapshots are consolidated.  I know starting with esx 5.0 U1, this became a manual process to perform (vmkfstools or esxcli storage unmap)....is this still true as of esxi 6.0 and 6.5?

Thanks in advance

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3 Replies
Punitsolanki
Enthusiast
Enthusiast

Need for space reclamation will be needed of there are following situation.

1. If there is a thin lun from the storage and you have deleted few vms or did a storage vmotion.

2. Esxi host does not do auto spce reclamation because it is an over head for hostd and vmkernel.

3 if you have VAAI feature then it can happen automatically because host will offload the task to the storage.

Punit Solanki psolanki@vmware.com
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senthilkumarms8
Enthusiast
Enthusiast

Hi,

Starting from vSphere 6.5 these reclamation tasks are automated. with the HW version 11 the new SCSI adaptor will send the unmap command to guest OS and if the guest OS supports this unmap it will work.

We have a GUI option to unmap the datastore unused space. also, you can set the interval how frequent this unmap should run.

Hope the following article will help you to get more details on this

https://storagehub.vmware.com/#!/vsphere-storage/vsphere-6-5-storage/unmap

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Nick_Andreev
Expert
Expert

Hi supermanDan,

Further to your question. Guest OS UNMAP is supported for Windows Server 2012 and later with VM hardware version 11 and for Linux with VM hardware version 13.

Hope that helps.

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