In this article, we are going to consider the storage pre-allocation aspect of virtual disk settings in detail and find out what thick and thin provisioning are, how they differ, and which of these storage pre-allocation types is better for your infrastructure. Thick provisioning is a type of storage pre-allocation. With thick provisioning, the complete amount of virtual disk storage capacity is pre-allocated on the physical storage when the virtual disk is created.
A thick-provisioned virtual disk consumes all the space allocated to it in the datastore right from the start, so the space is unavailable for use by other virtual machines. For data security reasons, eager zeroing is more common than lazy zeroing with thick-provisioned virtual disks.
When you delete a VMDK, the data on the datastore is not totally erased; the blocks are simply marked as available, until the operating system overwrites them. If you create an eager zeroed virtual disk on this datastore, the disk area will be totally erased i.
Thin provisioning is another type of storage pre-allocation. A thin-provisioned virtual disk consumes only the space that it needs initially, and grows with time according to demand. Thin-provisioned virtual disks are quick to create and useful for saving storage space. The performance of a thin-provisioned disk is not higher than that of a lazy zeroed thick-provisioned disk, because for both of these disk types, zeroes have to be written before writing data to a new block.
Note that when you delete your data from a thin-provisioned virtual disk, the disk size is not reduced automatically. This is because the operating system deletes only the indexes from the file table that refer to the file body in the file system; it marks the blocks that belonged to "deleted" files as free and accessible for new data to be written onto. This is why we see file removal as instant.
If it were a full deletion, where zeroes were written over the blocks that the deleted files occupied, it would take about the same amount of time as copying the files in question.
See the simplified illustration below. Using thin-provisioned virtual disks is not always smooth. There are some issues that you should be aware of and prepared to deal with. For example, we have a 20GB datastore with three virtual machines running on it. 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. In our case, 10, MB is the amount of free space that we want to fill with zeroes, so the number of 1-Megabyte blocks is This is where you should indicate the source from which you want to copy data.
After executing the above command, the size of our VMDK file grows. This is the output we see after the successfully completed command:. This means that almost the whole root partition i. This is because we have filled most of the previously "available" space with zeroes.To change the provisioning of a virtual machine base disk from thin to thick from the Datastore Browser :.
If the disk provision type is Thickdisk provisioning has already taken place. In this case, the disk provisioning is Thin. NOTE : if the Inflate option is grayed out, it indicates that the virtual machine is not powered off or that it is not thin provisioned. There should be no snapshots and the conversion is performed on the base disk. To convert a virtual machine base disk from thick to thin provisioning by changing the datastore and performing storage vMotion :.
NOTE : This process requires more than one datastore and enough space available. If only a single datastore exists, you can clone the virtual machine to a destination machine with thin provisioned disks instead of migrating. During migration of VM disks between storages, you can also change the type of the disk. In our case the type of virtual disk is Thick provision lazy zeroed.
Click Next. The method of changing disk provisioning type using CLI involves copying current vmdk file to a new thin provisioned disk and removing old thick disk.
At first, you should power off your VM. We are interested in the file w10rtm-test. To convert this file from Thick to Thinrun the following command:.
After the convertation is completed, delete the original Thick disk file w10rtm-test. Primary Menu Skip to content. Search for:. Secondary Menu Skip to content. To totally unlock this section you need to Log-in Login To change the provisioning of a virtual machine base disk from thin to thick from the Datastore Browser : Power off the virtual machine. In vSphere Clientright-click the virtual machine in the inventory. Click the Hardware tab and select the appropriate hard disk in the Hardware list.
Click Cancel to exit from Virtual Machine Properties dialog box. Click the Summary tab of the virtual machine. Under Resourcesright-click the datastore where the virtual machine resides and click Browse Datastore.
Double-click the virtual machine folder to display the. Right-click the. The Inflate option converts the disk to thick provisioned. Reload the. From Thick to Thin To convert a virtual machine base disk from thick to thin provisioning by changing the datastore and performing storage vMotion : NOTE : This process requires more than one datastore and enough space available. Right-click the virtual machine, and click Migrate. Click Change datastore. Click Nextand select a datastore that is not the same as the current datastore.
From the dropdown, select the Thin Provision virtual disk format. Click Next, then Finish. You can monitor the progress of the conversion in the Tasks and Events view in vCenter Server.This is a discussion that comes up regularly, going way back to vSphere 4.
Changing thick or thin provisioning for VMDK (VMware HDD)
The whole point of thin provisioning, whether done on the array or at the hypervisor layer, is to allow a VM to run with just the storage it needs, and to avoid giving a VM storage that it might use sometime in the future. After all, you're paying for this storage, so the last thing you want is to be paying for something you might never use. Thin — These virtual disks do not reserve space on the VMFS filesystem, nor do they reserve space on the back-end storage.
The Guest OS believes that it has the maximum disk size available to it as storage space from the start. Although they are called thick disks, they behave similar to thinly provisioned disks. This disk type may take a little longer to create as it zeroes out the blocks, but its performance should be optimal from deployment time no overhead in zeroing out disk blocks on-demand, meaning no latency incurred from the zeroing operation. However, if the array supports the VAAI Zero primitive which offloads the zero operation to the array, then the additional time to create the zeroed out VMDK should be minimal.
Option 1 — Thin Provision at the Array Side. The advantage is physical disk space savings. There is no need to calculate provisioned storage based on the total VMDKs. Storage Pools of 'thin' disks which can grow over time can now be used to present datastores to ESXi hosts.
VMs using thin or lazyzeroed VMDKs will now consume what they need rather than what they are allocated, which results in a capex saving no need to purchase additional disk space. In most cases, it simply a matter of dropping more storage into the pool to address this, but of course the assumption here is that you have a SAN admin who is monitoring for these events. Option 2- Thin Provision at the Hypervisor Side. In no specific order:. Thin Provisioning Concerns. VMs which do not require additional disk space continue to run quite happily even though there is no space left on the datastore.
First, Eagerzeroedthick VMDKs do not lend themselves to thin provisioning at the backend since all of the allocated space is zeroed out at creation time. This leaves us with the option of lazyzeroedthick, and this works just fine on thin provisioned devices.
One of the very nice things about this appraoch is that, through the use of Storage DRS, when one datastore in a datastore cluster starts to run out of space, possibly as a result of thinly provisioned VMs growing in size, SDRS can use Storage vMotion to move VMs around the remaining datastores in the datastore cluster and avoid a datastore filling up completely. This is the option I get the most queries about. Wouldn't this give you the best of both worlds?
While there is nothing inherently wrong with doing thin-on-thin, there is an additional management overhead occurred with this approach.
While VAAI has introduced a number of features to handle over-commitment as discussed earlier, thin provisioning will still have to be managed at the host hypervisor level as well as at the storage array level. But keep in mind that this level of over-commitment could lead to out of space conditions occuring sooner rather than later. At the VMDK level, you once again have the additional latency of zeroing out blocks, and at the array level you have the space reclamation concern.
With all this in mind, you will have to trade off each of these options against each other to see which is the most suitable for your environment. How much space does a thin disk consume?Cirugia nano capilar
I may have missed some pros and cons to of some the options listed above.I do not know a single system where you do not have at least 10GB of free space for OS disks. A common issue with thin disks is that the size will grow when required, but never shrink. This post describes how to reclaim unused space from the virtual machine. Windows does not automatically zero deleted blocks. Microsoft provides a tool that can zero blocks after while deleting a file or zero out the entire free space.
This is required to reclaim space back from the virtual disk. Wait a couple of minutes until the process is finished. Please note that you virtual disk file VMDK will grow to the full size during the process. There are various tools available to create zeroed blocks. The best known tool is dd which should be available on all systems. Excellent post! I am going to do this on a volume that is 1.
I need to build a communication for the environment on how long the VM will be down. Hi, Josh. You can do it completely without downtime with Extrasphere disks not VM migration to another datastore even on free licensed ESXi host.
Thanks for sharing this useful info. I have a question after applying these steps. Please let me know how I can reduce this size as well? Any help is highly appreciable. Than You. Once you migrate to another host the provisioned storage reflects the shrunk size so migrate to another host and back again. Note: without vMotion you'll need to have the VM powered off for the duration. Provisioned storage is the amount of space the disk can grow to.
So it's correct that it does not decrease when shrinking disks. Sorry, typo.Not sure if this is the right forum. But I have a question about copying thin provisioned vmdk files. I created a VM on local storage for the time being and wanted to copy the files off that and move to another host's local storage just temporarily until shared storage is in place. It is a VM with two 20gig thin provisioned drives. One has like 8gb worth of used data the other about 1gb. I tried doing the copy through the VI client and by browsing the datastore and uploading the files to my local PC.
Thick and Thin Provisioning: What Is the Difference?
Then I was going to copy them to the other host's local storage I wanted to put them on. I noticed when copying the files from the datastore to my PC they came down as the full 20gb vmdk. Is this normal and will it still be thin provisioned when I copy it back to the other host?
Server Fault is a question and answer site for system and network administrators. It only takes a minute to sign up. I wanted to give myself a head start so I began setting an ESXi environment inside VMware Workstation 8 to create a base installation of Windows to copy. My thought was that it would be fairly easy to just bring the vmdk to my next class and upload it to our ESXi machine. But as I began downloading the vmdk disk image from my ESXi server in vmware, I noticed that it took a very long time.
On closer inspection I found out that the vmdk was taking up 40 GB of space even though it is setup to do thin provisioning and the Windows installation only took about 7 GB.Yt9216b
How can it be that the image is so large when I attempt to move it? Take a look at this VMware Communities thread for a solution. I found a way to solve my problem. Simply enable the ESXi shell and tar. Then I could download each tar. It might not be that usable in a running server environment because you have to shut down the servers to tar.
Thanks for the suggestions though. You can also migrate from thick- to thin-provision disks this way. Sign up to join this community.Will strobe lights get rid of rats
The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 8 years, 6 months ago. Active 5 years, 7 months ago. Viewed 8k times. Zoredache k 32 32 gold badges silver badges bronze badges. Active Oldest Votes. This worked for me, however upon unpacking the tarball it loses its thin provisioning.
May 27 '15 at Jim G. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Socializing with co-workers while social distancing. Podcast Programming tutorials can be a real drag.
Featured on Meta. Community and Moderator guidelines for escalating issues via new response….I'm running ESXi 6. Current used space is less than GB and isn't going to grow beyond that. This is a production server, so the utmost care must be taken. There are 4 other drives on this virtual server and they are all fine with their respective sizing. Is it possible to shrink that overly large disk and recover the unused LUN space?
Copy the data over to this using something like Robocopy. When ready, switch the drive letters and move on with life.
Does VMware Converter run a type of clone command against the original virtual machine, allowing you to change some aspects of the resulting virtual machine? Or does it modify the existing virtual machine with no backout plan? Only ever ran the P2V version and that was years ago I suppose I can do some copy tests and see how long it would take to copy and use this method.
So no downtime with a failsafe process? Would a 15 minutes downtime be acceptable? That converts the vmdk from thick to thin. If you want to do a partition resize let me know. Downtime outside of business and reporting hours is acceptable, I have a decent window for maintenance and such. I'm assuming the "vmkfstools" command needs ran from the particular hosts console? Upon completion, the space differential between what is fully allocated now as a thick disk vs what is being used will be automatically available to the VMware environment?
Since these are Windows partitions, once the steps you listed are completed, is there anything else that is needed to be done to the Windows OS for the partition to show correctly? So I tested the VMware Converter Standalone product and while it worked, it took it's own sweet time, and maybe that is due to how I have it setup.
While the process worked, it took about an hour and 45 minutes. Would this process be sped up if the Converter application was installed on a guest server that is part of the VMware environment?
Converter will always be one of the slowest options Just had another idea Why dont you add a new GB vmdk to that VM and then use robocopy to copy the data to the new drive. Then you just need a short period without activity to do a final sync and then switch driveletters so that the new disk gets the driveletter of the old - large vmdk.
I've thought about that idea, of using a new drive and RoboCopy.
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