VMware 5.0 - Failed to extent swap


Im trying to start a VM and Im getting the following error (error_1 attached).

I dont undertand where exactly s the problem since I still have 800MB free in the datastore assigned to this VM... which are the data_ds1 and the vm_ds1.

I believe the issue is somehow at the vm_ds1. (but it has 4G free - see disk_2 attached)

The sum of space used among the VMs that shares this datastore doesnt reach its maximum capacity...  (prints attached)

The VM swap location has to be in the same directory of the VM since it is in a cluster.

Anything I might be missing/misunderstanding?

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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Every time you power on a VM, a SWAP file is created equal to the size of memory, or the reservation if any set in the VM.

If you do not have the space available on the datastore, the VM will fail to start!

This VM needs 4GB, so you must have 4GB available on the datastore.

Your datastores are terrible low, you must allow at least 20-25% FREE on the datastore, to allow for SWAP files and Snapshots if applicable, otherwise VMs will fail.


1. Relocate the VSWAP file to another datastore with space.

2. Move the VMs to another datastore with space.

3. Increase the size of datastores.

see here


joaotellesAuthor Commented:

I will try to move the VMs to another datastore with space. I get back tomorrow with the result.

Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Okay, let me know.

You should not really run your datastores that low!
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joaotellesAuthor Commented:
I moved it and its working but still I have like you said very low datastore. I may have to delete some VMs in order to have the 20-25% you mentioned its ideal.

By now I have this: (attached summary report)

I have a couple of question regarding the calculation how much space does a VM take if its ok for you before I close the post:

1- The amount of memory the VM needs to startup is the amount of memory it has assigned to it right? so 4G of memory means that it will need 4G of datastore space as long as its running. Is this correct?

2- What memory overhead means in the VM summary.. I couldnt get it... Is it the amount of memory it can extend to?

3- I have a VM that takes 25G of Used storadge from one of the datastores. But it has 115G of Provisioning space. But the datastore assigned to it has 125G. I can be mising everything up but is there any relation between these three parameters? (used storadge, prov space, datastore capacity)

4- In the storadge view, for some I have a Snapshot Space of some G's and for some others its just 0.00B. Can this be related to the lack of space in the datastore?

Tks and sorry for so many questions...

joaotellesAuthor Commented:
Also (one more Im sorry)

5- This is probably the most silly question, but the space used by a VM seen in the vSphere, does it change if I delete OS files from the VM itself or this used space is a fixed space used by the VM no matter how many files it has. For eg. if the used space in the VM is 20G and I delete 5G of OS files from the VM, should the Used space shrink to 15G right way?

Tks again,
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
1. Correct, everytime you start a VM, a vSWAP file is created equal to memory in the VM, or it's memory reservation. So a 4GB RAM VM, needs 4GB on the datastore.

2. This is the memory, required in the host, to run your VM. So 4GB RAM VM, 4GB assigned to VM, but the host, needs some memory to run this VM.

3. Datastore Capacity is the maximum datastore space. Provisioned is what is assigned to the Virtual Disks in the VM.

4. Correct. See my EE Article on Snapshots, Snaphots are not good to have!

HOW TO: VMware Snapshots :- Be Patient

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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
5. No. Because when you create a virtual disk with NO OS or files, it still takes up 25GB on the datastore. Deleting files in the virtual disk, does not change it's size.
joaotellesAuthor Commented:
Tks! I will go through your article.

Regarding the #5, is there a way to resize the VM size? And I couldnt find in the vSphere a place to check the the amount that the VM is using of these 25GB that is assigned to it in the datastore.

Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
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