VMWare datastore storage space

The first thing to check is...

1. Snapshots, is the VM running on a snapshot ?

2. What is the disk, thick or thin ?

3. What size did you make the VMDK size for the Guest OS ?

4. What is the size of the datastore ?

Did you leave 20-25% working overhead on the datastore ?

Hi Andrew,

Hope you are well. In answer to your questions.

1. No the VM is not running on a snapshot.
2. Disk is Thin
3. VMDK size is 14.8 TB
4. Datastore size is 15TB
5. This disk did originally have plenty of overhead, however as the disk is used for backups has grown, I cannot increase the back end stroage beyond 15b and therefore cannot increase the datastore size (without spanning volumes, which i dont want to do). On the server side, the disk has nearly 6tb free, the datastore only reports 1.39tb free.

As always thankyou for your help.

Cheers,
Paul

That's the issue, in you've created a 14.8TB virtual machine disk, with a datastore size of 15TB.

The virtual machine disk was created too large to start with, and you really need to give space for the overhead of at least 20-20% of the datastore (by experience for snapshots, swap files, and other misc)

It's maximum size, when fully inflated will be 14.8TB on the disk, and if you format the virtual machine disk, when created thin it will occupy all space.

it does not matter if you only have 6TB free in the OS.

options,

1. Increase the datastore size.
2. Reduce the size of the virtual machine disk, which to do it means use VMware Converter to SHRINK the disk to a size of e.g. 10TB, which will recover 4TB, and make it a FIXED thick disk.

see my EE Article here, and download 6.2.1 of Converter.

HOW TO: Shrink or Reduce a VMware Virtual Machine Disk (VMDK) using VMware vCenter Converter Standalone v5.5.2

Hi Andrew,

Apologies for the extra questions. So as I understand it becasuse the VMDK is a thin disk, at some point within the guest VM the hard disk mapped to this from Windows perspective used up all of the space inflating the disk. This space was then released by the operating system, but this space is not released from within the virtual disk and the datastore. Wouldnt this mean then that the Disk within Windows can grow again to this size, without effecting the size of the vmdk/datastore (blocks that the vmdk/datastore has currently marked as written, that arent used by the guest are now overwritten)?

Secodnly if a datastore reports as being at capacity, but the guest within the datastore, has plenty of space, I am assuming nothing bad happens. The server will continue to work (as it has space), and VmWare will send me emails stating the datastore is full?

As the disk is attached and used for backups, I am not sure I will have enough of a window to convert the disk and resize, without the backups either interferring, or getting out of synch. Nor can I easily increase the datatsore size, as the back end SAN wont allow me to increase the existing volume. Is there no other way to reclaim the space back?

If not i guess i will need to look at recreating some of the backup jobs and migrating them over to a smaller disk at some point.

Thanks Again,
Paul

Hi Andrew,

I am really sorry, just a few more questions.

As the disk didnt start off that size, but was extended both at the datastore and within windows. Does the same thing occur when extendending through windows, whereas the extended part of the windows volume will be filled with 1's therefore the thin disk will automatically grow by this size. If that being the case, wouldnt it be simpler on volumes that are expeted to grow on a regular basis to use thick disks instead?

Secondly if the thin disk is inflated as soon as the hard disk is formatted on the guest, dosnt this make thin disks a bit pointless, unless they are always just about there size wise?

Unfortunatley I dont have another datastore that will be big enough to migrate to, I will need to look at re organising the backups.

Apologies for the newbie questions, and I reall do appreciate your help.

Kind Regards,
Paul

As always many thanks, think i will be using more thick disks in the future :)

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