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06-20-2013 09:42 AM
All the HP documentation regarding snapshots say they are thin provisioned and consume no additional space at the point it's taken. I understand disk space is used when the data changes afterwards.
But after a call with HP, they are telling me snapshots are only thin provisioned when the source volume is thin provisioned. If the volume is full provisioned and the amount of data uage is 60GB within a 100GB full prov volume, then the snapshot will immediatly start at 60GB (totaling 120GB).
This is very misleading from what their documentation states and is very dissapointing if true.
Has anyone else seen this in their environment?
06-20-2013 10:10 AM
yes you are correct that is what happens.
On the flip side, there is little reason not to make your volume thin-provisioned. if you insist on thick, just make it thin and then do a full format or drive wipe which will expand it and it gets you the same effect and still let you use thin provisioning for snapshots.
06-20-2013 10:40 AM
A direct quote from HP documentation-
What makes P4000 Snapshots unique is that they are
thin-provisioned volume copies that require no space reservation
To go from this to the reality of only on volumes that are thin provisioned is absurd!
You can't implement enterprise virtualisation storage using thinly provisioned volumes, there is simply too much to go wrong.
Thanks for your comment oikjn
06-20-2013 03:03 PM
Four out of five of the largest service providers in the world use HP 3PAR, and the reason they use it is because of all the autonomic features including thin provisioning that allow saving management time while saving physical hardware resources.
I know personally that one of the largest national server outsourcing companies uses HP P4000 storage, setup to best practices with thin provisioning enabled, and offers 5+ 9s of uptime.
In fact, I'd argue the exact opposite - there's no competent enterprise in the world that DOESN'T use thin provisioning and other automated features to optimize their storage environments.
There's more likely to go wrong by not using thin provisioning and by forcing the necessity for manual intervention to manage LUN sizes.
Just my 2 cents.
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06-21-2013 02:33 AM
One could argue it's not possible to manage your storage if you have multiple volumes configured as thin provisioned because there is no way to stop a user/ service filling up a volume at any given time.
You cannot manage that.
The pro's and con's of thin and full could be argued all day, everyones environment and business requirements are different.
The point here is HP advertsising something that is only true with a specific condition yet they word their marketing differently. The fact that there is a hugely significant difference in the amount of storage used for a snapshot depending on whether the volume is thin or fully provisioning should be clearly documented.
I can't find anywhere in HP'sdocumentation- user guides, deployment guides etc where this is mentioned, not a single place. Something as important as this should be clear and consise. Sadly, this is not the case.
I've had to find this out by wasting hours of my time with HP on call support. This should not be the case.
06-21-2013 09:40 AM
I'm w/ david here. There is a difference between thin provisioning and over-provisioning. You can do thin provisioning and not over-provision the volume. Just look at your cluster use summary and as long as your provisioned space+thin provisioning saving doesn't add up to more than your total storage space you are not over-provisioned.
Also, I believe every snapshot takes up at least 1GB space (but that might just be reprting space and not actual space).
Again, if you are insistant on full, you can simulate a full drive by simply making a thin drive and then filling the drive with data and then erasing it which would expand the drive completely.