Windows 2012 Auto Grow Volume

I know some Storage will auto grow as needed.  But will Windows see that and grow as well?  That has not been my experience, I have always shad to go and 'extend' the volume.  And TechNet links would be helpful.
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Cliff GaliherConnect With a Mentor Commented:
Windows will *NOT* automatically extend a volume.

HOWEVER, in most cases  where storage that supports "auto grow" as you put it, such as dynamically expanding disks in Hyper-V, the drive presented to the OS is already the appropriate size.

For example, in Hyper-V, you'll create a dynamic expanding disk and set the theoretical size of the drive. The default is 127GB.  Hyper-V will then create file that is nowhere *near* 127GBs.  A few megabytes is all.  Then the guest OS will "see" a 127GB drive and you can create that as a full 127GB partition. But the physical VHDX file is still just a few megabytes. As you copy data to the drive. Hyper-V will expand the physical file to hold the data. But since the guest OS already saw a 127GB drive, it doesn't need to expand the partition.

And when you reach 127GB of actual data on the drive, Hyper-V will not expand the file further. So the partition also will not expand.

If you go and edit the drive, and make it larger, it'd be just like replacing a drive in your physical computer and backing up and restoring the partition(s) onto the new drive. The excess new space is unallocated and would need to be allocated in disk manager like any other.
Gerald ConnollyConnect With a Mentor Commented:
What Cliff is describing is Thin provisioning.

What ever you use, you always need to monitor the free space on your disks/volumes/data stores.

If you monitor the free space its easy to draw a graph and work out when you will reach a specific thresh-hold (say 95% utilised) and either archive some of your data to release space (i am assuming you are actively managing your used space with something like windirstat) or expand your file space by adding more/bigger disks.
loftywormAuthor Commented:
Ty, that is exactly my experience.

BUT what if the disk is presented like an iSCSI disk, or LUN?
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Gerald ConnollyCommented:
Managing your storage is SOP

Everybody managing a system needs to do this
loftywormAuthor Commented:
I agree.  But I am the new guy, and I am not sure how they do things exactly yet.  I think this is a problem, but I am told it will auto grow.   I don't believe them, but I need to be certain.
Philip ElderConnect With a Mentor Technical Architect - HA/Compute/StorageCommented:
iSCSI Disk is delivered via a storage backend. The storage will have the configuration logic set up on it. Log on to the storage console and have a look at the way the LUNs are set up.
kevinhsiehConnect With a Mentor Commented:
As far as the OS is concerned, it knows nothing about thin or thick provisioning, be that via hypervisor or SAN storage protocol (FC or iSCSI). If you need to expand a filesystem, you need to extend the partition. That has always been the case.
loftywormAuthor Commented:
TY for the validation!!

To clarify, I am talking ONLY about the Windows Volume, not the storage side.  I know storage can dynamically, the question is will Windows see that dynamic growth, and use it (Even if the entire disk is presented via LUN).  

The answer is, "No".
Gerald ConnollyCommented:
lofty, If your storage is Thin Provisioned, Windows will not be aware, and the answer is YES
loftywormAuthor Commented:
I am not following you Gerald;
Question: Will windows use any dynamically expanded space?
Windows will not be aware.
Then how can the answer be yes?
Gerald ConnollyCommented:
For a thin provisioned partition say of 1TB, Windows thinks its 1TB, but the actual physical utilisation could only be 1GB, if you physical data store/Disk has 1TB free then the physical useage of the partition will dynamically expand as the useage goes up. Its only when the utilised space reaches the provisioned space is management required.

Taking this further, its easy to allocated say 3 x 3TB thin partitions to a single 1TB physical disk and its only when the physical useage of all three approach 1TB would any management be required.

another way to use thinly provisioned partitions is to overprovision a partition say to 10TB, but actually only have 1TB of physical disk underneath it, as you know you only initially need 200GB and that your data growth is 100GB/month - that means you have approx 7 months before you run out of physical disk and if you then expand the physical disk you can have 10+ years of data growth without having to touch Windows

In either case until the physical storage runs out Windows is complete unaware of what
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