VM grew to 258GB on datastore formatted with a 1M block size

[daveclaussen]

I have an ESXi 4.1 server (VMFS 3.33) , stand alone, older server, hosting a single VM. When I created the server, I made the local datastore a 1MB block size because the VM would never grow above 256GB. As of a few days ago, our backups started failing with the following message:

Create virtual machine snapshot vmname

File  vmname.vmx is larger than the maximum size supported by datastore

I checked the VM files and the vmname.vmdk file was more than 256GB.

I cannot storage vMotion this VM somewhere else being a standalone server, I cannot add storage to this server as it is old and has no more room for hard drives. I guess my only option is to do an in place upgrade of this host to ESXi v5.1 and have the VMFS level go from 3 to 5. I am hesitant to do this with no good backup for at least a week.

Anyway, does anyone know HOW this VM grew to greater than 256GB in the first place? How is it still running if the system should technically not be able to recognize the file(s)?

Thank for your time all.

- Dave Claussen

[vmroyale]

Where are you getting the 258GB number from - the datastore browser?

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&e...

has info on VMFS overheads behind this and the workarounds you can use.

Upgrading to VMFS-5 won't help, because the 1MB block size would be retained as part of the upgrade.

[daveclaussen]

From your link...

Note: On ESXi 5.x hosts using VMFS5 upgraded from VMFS3, the upgraded volumes inherit the VMFS3 block size.

The default block size for new volumes is 1MB. The maximum file size, regardless of block size, is 2TB - 512Bytes.

While it does retain the 1MB size, on VMFS 5, that is the default and a VM can be up to 2TB.

[vmroyale]

Upgraded VMFS-5 volumes inherit and maintain the VMFS-3 block size and the size limitations that go along with the VMFS-3 block sizes. Those are listed in the kb.

The default block size for new VMFS-5 volumes is 1MB. The maximum file size, regardless of block size (new or upgraded), is 2TB - 512Bytes. This means that VMDKs greater than 2TB minus 512 bytes are not possible.

[daveclaussen]

Ok - I got it now. Well, I guess I am screwed. The only thing I can think to do is copy the VM to an external drive, upgrade the host and copy it back.

Do you know how this file, at 258GB, can even work on this 1MB block VMFS3 datastore?

[Kurt1]

As vmroyale noted: http://kb.vmware.com/kb/2003813
You get what you had when you do a straight upgrade. You could try using the datastore browser to download the VMDK-flat file to your workstation / USB drive, etc.

If I was going to guess about the "how" I would say that some file/set of files were allocated simultaneously which created the overage. Also, if the block indirection was slightly more efficient than promised perhaps that would account for the 2 MB overage you are seeing.

[vmroyale]

Do you know how this file, at 258GB, can even work on this 1MB block VMFS3 datastore?

Where are you getting this value from?

256GB = 262144MB = 268435456 KB

Different places (vSphere Client's datastore browser, ESXi Shell, etc) report different units of measure.

[daveclaussen]

vSphere client shows 258GB

Datastore browser shows 267,386,900.00