VMware Cloud Community
TheVMinator
Expert
Expert

Should Virtual Machines be powered down before removing snapshots?

Suppose I discover a high transaction volume virtual machine with a very big, very old snapshot disk.

Is it recommended to power off the virtual machine before committing the snapshot?  What factors make powering down a virtual machine before removing the snapshot to be important?  How big, how old, how much i/o makes this necessary?

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5 Replies
Borja_Mari
Virtuoso
Virtuoso

Hi,

you can consolidate the snapshot while the virtual machine is powered on or powered off.

If this virtual machine has high I/O, then (if it possible) maybe the best option is consolidate the snapshot while the vm is powered off. Because if it's powered on, the last step in the snapshot's consolidation will turn the vm stalled.

Anyway, if the vm is powered off, it remains inaccessible all the time, hehehe

Smiley Wink

Hope this helps Smiley Happy

Best regards,

Pablo

------------------------------------------------------------------------------------------------- PLEASE CONSIDER AWARDING any HELPFUL or CORRECT reply. Thanks!! Por favor CONSIDERA PREMIAR cualquier respuesta ÚTIL o CORRECTA . ¡¡Muchas gracias!! VCP3, VCP4, VCP5-DCV (VCP550), vExpert 2010, 2014 BLOG: http://communities.vmware.com/blogs/VirtuallyAnITNoob
TheVMinator
Expert
Expert

OK thanks.  How do I determine how much I/O a VM has to have before removing a snapshot is a risk while the VM is running?

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Borja_Mari
Virtuoso
Virtuoso

Hi,

it depends, there isn't a unique answer to your question.

As i commented before, a virtual machine with high I/O, will remain stalled in the last step in the snapshot consolidation.

if the the disk where the vm has its vdisk has good performance (for example 10-15K SAS disk), the vm should be stalled just for a short time.

To check the number of I/O operations in the vm, you can use the advanced performance charts.

Select "virtual disk" and then on "charts options", select "Average read requests per second" and "Average write requests per second"

If the vm has just a few I/O operations, the snapshot consolidation should be quickly.

If the number of I/O increases, then the the snapshot consolidation time should increase too.

Best regards,

Pablo

------------------------------------------------------------------------------------------------- PLEASE CONSIDER AWARDING any HELPFUL or CORRECT reply. Thanks!! Por favor CONSIDERA PREMIAR cualquier respuesta ÚTIL o CORRECTA . ¡¡Muchas gracias!! VCP3, VCP4, VCP5-DCV (VCP550), vExpert 2010, 2014 BLOG: http://communities.vmware.com/blogs/VirtuallyAnITNoob
TheVMinator
Expert
Expert

Thanks for your input.  I think I'm more concerned about corruption or longer-lasting problems than I am from the virtual machine failing to respond temporarily as long as data isn't lost.  If there is a risk of these kind of problems under "High I/O", then I wouldn't know when to be concerned unless I knew what "high I/O" was -  50 IOPS? 100 IOPs? 200 IOPs?  If someone has an opinion on this I'm open for suggestions, experiences, etc.

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Borja_Mari
Virtuoso
Virtuoso

Hi,

based in my experience, a vm running in a standard/normal disk with an average IOPS of 50/sec (maximum 80), remains stalled around 30 minutes in the last step of the snapshot consolidation.

AFAIK, never i had seen corruption in the snapshotting process. You shouldn't worry about this Smiley Wink

I recommend you check this vmware's KB about snapshots (in this order):

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100283...

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100756...

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100756...

Best regards,

Pablo

------------------------------------------------------------------------------------------------- PLEASE CONSIDER AWARDING any HELPFUL or CORRECT reply. Thanks!! Por favor CONSIDERA PREMIAR cualquier respuesta ÚTIL o CORRECTA . ¡¡Muchas gracias!! VCP3, VCP4, VCP5-DCV (VCP550), vExpert 2010, 2014 BLOG: http://communities.vmware.com/blogs/VirtuallyAnITNoob
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