How to enable snapshots on CX4-480

Mike,

have you considered using Hyper-V snapshot functionality. This would give you ability to "undo" the changes that were made to the OS. If you use Clariion snapshot functionality, you would have to roll back the whole LUN that could possible contain multiple VMs ..probably not what you want to do.

Hello Dynamox,

thanks for that hint.

As I have very limited knowledge about the Microsoft Hyper-V stuff, I just asked one of the admins who work with the Microsoft server/cluster/hyper-V.

He told me:

We don't want to go for MS Hyper-V snapshots due to the following facts:

(Note: I am just citing input I got from the colleagues, not claiming that it is 100% correct)

a) we want to have the snapshots automatically created (because people tend to forget to take a snaphot if it needs to be done manually) and deleted in specified time intervals

b) Snapshots on Hyper-V are painfully slow

c) A Hyper-V VM which has a Snapshot can not merge to another server in case of problems

I have a gut feeling that in addition to the facts above, they don't trust Hyper-V snapshotting that much ;-)

(We in the IT dept. wanted to go for VMware but the number-crunchers insisted on Hyper-V)

What we hope to get with snapshots on the EMC:

It happens from time to time that a hotfix destroys a installation or something else causes problems.

So if for example, a problem happens to a VM at 12:00 we want to be able to go back to the state at 10:00 (where the snapshot was taken).

kind regards

Mike

what they are asking is doable, the thing is ..if you have 10 VMs that reside on one LUN, you can't just roll back one particular VM, you have to roll back all 10 VMs. Yes, you could present this snapshot/clone to another Hyper-V server and import that LUN and try to recover that particular VM but do you want to do that every time they have an upgrade/patch that did not go well. Second thing is you will need to invest in some tools like Replication Manager that will provide you with application/OS consistency, otherwise you get a crash-consistent copy of your VM, as if somebody pull the power cable on the server. To me snapshots/clones are good for major issues with VM stores, like file system corruption but for ability to roll back patch installed, application upgrades ..i would still look into hypervisor functionality. My 2 cents

Hello Dynamox,

thanks a lot for your very good explanation and for having that discussion with me.

So it seems there is no  really "good" solution (neither on EMC level nor on Hyper-V level) as when using Hyper-V snapshots, I have

- the problem that if a virtual machine has a snapshot it can't be migrated (manually or automatically, e.g. in case of a server problem)

- there is no comfortable way to schedule creation and deletion of the snapshots

- the Hyper-V snapshots consum a lot of space (much more than on storage level)

- the snapshots take a lot of time

and when using EMC-level based snapshots we have the drawbacks that

- Snapshots are LUN-based which means that rolling back will roll back all VMs (if more than one is in one LUN)

   The consequence would be to have a exclusive LUN for all VMs where they want to use the EMC-based snapshots which leads to the question of how much LUNs can I have on a cx480....

- Snapshots are not application/OS consistent (which is new to me) and so I have to purchase SnapView AND Replication Manager if I want to get app/OS consistent snapshots (hope, I understood you well in this point).

Discussing that with the software guys, they kept insisting to have snapshots on EMC level rather than on Hyper-V.

My boss joined the discussion and remarked that having application/OS consistent snapshots automatically done on EMC level was one of the key features we outlined in the requirement specification and 2 EMC representatives (EMC Germany) claimed that this will be nice and easy.

Now my boss and the software guys want me to make it work exactly that way (whatever it may cost).

Our supplier's support is horrible (despite us paying tons of money for the design, installation and integration service), meanwhile I doubt he has any certified (really skilled) technician. As our supplier is one of our valued customers, I am not allowed to battle with them over the lack of support and so I am on my own now.

So I am grateful for the insight you offered and learned some but am back to the original question of how I do get to app/OS consistent snapshots :-(

kind regards

Mike

Mike,

take a look at this document, specifically page 21

White Paper: Using EMC CLARiiON with Microsoft Hyper-V Server  Applied Technology

if i understand that section, Replication Manager is only supported with iSCSI attached LUNs or LUNs in pass-through mode. To me it looks like you could create a solution with using "admsnap flush" and navicli commands where you first execute admsnap commands on the host and flush the buffers and then you create the snap. Although to me it's going to be an OS consistent snapshot, not an application consistent snapshot since you don't have any hooks into apps like SQL, Exchange or whatever else you run on your VMs. Maybe it satisfies your business requirements ?

http://www.emc.com/collateral/software/data-sheet/c848-replication-manager.pdf

Hi Dynamox,

thanks for the information, I will read it.

Next week I am on vacation and read it when I'm back.

thanks and kind regards

Mike

There is a seperately-licensed VMware snapshot (for VMFS) feature in RM - it is pretty pricey and didn't think it was worth it in our case (we just use VMware snapshots on an adhoc basis when doing major changes).  The whitepapers lag a little with RM so you might want to check the release notes/admin documentation to see if there are any good nuggets in there specific to HyperV.  Pretty sure there were some major changes to the shared file system in R2 perhaps RM has something new to take advantage of it.  RM is a good product but gets little fanfare.  I'd also check the changes in R2 for live migrations with snapshots as I think that may have changed as well...Microsoft is constantly playing catchup and a feature missing today is often slipped into the next release or even the dreaded "feature pack".

Dan