Netapp - recovering from out of space situation

Posted on 2012-08-18
Last Modified: 2012-08-19
Supposed that you had a 100GB LUN in a 200GB Volume on a 1TB aggregate.  Neither the LUN nor the volume are set to auto-grow.  The LUN has been sitting at around 70GB for months and then one night someone tried to copy a 50GB dump file to the LUN.  What is the impact of this to say a Windows VM that is using the LUN for storage?  Would the drive just disappear from Windows' perspective?  And if this happened in real life ( it hasn't I'm just trying to understand Netapp storage better - phew) how would one go about recovering from this faux-pas?  Just go in and resize the LUN and re-boot the VM?
Question by:amigan_99
    LVL 116

    Assisted Solution

    by:Andrew Hancock (VMware vExpert / EE MVE)
    LUN may go Offline, the datastore would not be available to the ESX/ESXi host server, and VM would likely still run, until it needed to write to the virtual disk, and at this point the VM would fail.

    Solution:- Increase the LUN size, Online the LUN, Rescan the HBA, Turn Off and Turn in the VM.
    LVL 21

    Accepted Solution

    If the LUN is being used as a VMware datastore, you don't want it to fill up. If this happens,  VMs will continue running, but operations like taking snapshots will fail.

    If the LUN is directly mounted inside the VM as a volume, copying a large file to the volume will simply fill it up, exactly like a hard disk that is full. Free up space from within the VM.

    Things get a bit more complicated if you use snapshots on the netapp volume. Each snapshot keeps modified blocks and eventually the netapp volume will fill up. If this happens, you could get write errors on the LUN or the LUN could go offline. Data will be lost!

    In that case, delete snapshots from the netapp volume or increase the volume size. From within the VM, mount the LUN again and perform a volume check to make sure everything is ok. The volume or data within may be corrupted!

    Netapp does have something called LUN space reservation to prevent this from happening. If your LUN occupies 70GB, it will reserve another 70GB to keep the LUN functioning correctly, even if the Netapp volume is full. If you disable space reservation, you should use a monitoring tool that alerts you that the volume is filling up.
    LVL 1

    Author Closing Comment

    Both really outstanding replies.  Thank you guys so much.

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