Vmware thin provisioning how does it work

Each virtual machine has a thin-provisioned virtual disk set with a maximum size of 10 GB. This practice is called "overprovisioning" — we assign virtual disks more space than they can physically take up.

This is done often, as it allows you to scale the system by adding more physical storage as you need it. The file size of each virtual disk will expand as data is added, until there is no free space left on the datastore. Regular methods of file deletion within virtual machines will not help shrink the thin-provisioned virtual disks.

If more than 1 GB of new data is written to any of these virtual machines, all three of them will fail, and you will need to migrate one or more of the virtual machines to another datastore to restore their running states.

To be able to reduce the VMDK file size of your thin-provisioned virtual disks, you need to know how to zero the blocks that the data you deleted previously occupied. NOTE : Disk shrinking operations are only possible if the virtual machines do not contain snapshots. Also, please be attentive and execute commands at your own responsibility. Always back up all of your important data before carrying out any disk operations. We can try to delete unnecessary files on this virtual disk.

However, Linux does not automatically zero blocks after deleting files; you will have to do this yourself. You can do this by using the dd data duplicator utility for copying and converting data.

This tool is available on all Linux systems. NOTE : Before running the dd utility, it is necessary to make sure the datastore has enough capacity to use it e.

When Steve Snyder and I chatted a couple of weeks ago, we agreed that one of the many hypervisor platforms out there will eventually come out with truly elastic provisioning. But neither of us has succeeded in finding any concrete news about this development.

Photo Credit: Bill Ebbesen via Wikimedia. Because of: Flexibility Savings With thin provisioning you can create multiple VMs virtual machines on a physical hard drive without worrying whether you have the space to cover it because your hypervisor will apportion only the amount of space the VM is using.

As commenter wazoox explains: [T]he performance hit is mostly fragmentation. The next step in that feature set is thin provisioning. Thin provisioning allows you to allocate a logical disk the same way, except that the storage reports actual usage of the bits in that disk rather than the fully allocated capacity. So a newly allocated 1TB disk uses zero actual disk space. Theoretically you could create hundreds of them on your 10TB physical disk and so long as you never actually used them, everything would be happy.

There are two places where thin provisioning can come into play. Both of these places can specify thin or thick provisioning independently of the other, assuming your SAN has the ability to do thin provisioning. The rest of this article is a discussion about the consequences of doing so assuming a SAN that can do thin provisioning and a VMware environment. If you are doing a combination of thin and thick provisioning between the SAN and VMware, your available free space will be different between the two, and may lead to some confusion.

The SAN is going to always report the real disk space you have used or free. It is the ultimate authority. If there is free space, you can write to the disks and allocate more disk. I can allocate that capacity to hosts as I please. In VMware, if you thick provision a G disk from a 4TB datastore, the datastore immediately reports 3. To continue this discussion, please ask a new question.

Get answers from your peers along with millions of IT pros who visit Spiceworks. Best Answer. Ghost Chili. Verify your account to enable IT peers to see that you are a professional. I think you are a little confused on thin provisioning. Clear as mud??!! View this "Best Answer" in the replies below ». Popular Topics in VMware. Spiceworks Help Desk. The help desk software for IT.

Track users' IT needs, easily, and with only the features you need. Learn More ». StorageNinja This person is a verified professional.