HPE Storage Users Group

Hi Guys,

I hope all are well. I have a very quick question that I am hoping you can help with. I understand that 3par is VMware MSC certified. If I wanted to offer zero RTO to a virtual machine in the case of a complete site failure (storage/network,servers, everything)... would I have to run VMware FT over the cross site VMware Implementation? Assuming of course all the requirments are met for Peer Persistence and Remote Copy to be implemented.


Thanks
Roo

Roo,

In order to offer a zero RTO for a vm, your best bet is going to be application level ha rather than at the storage/hypervisor level.

Vmware ft may get you there, but the technology has severe limitations that make it almost useless for a production server.

For true zero RTO, you need a distributed application a la web server farm, microsoft exchange DAG, etc.

Schmoog

Nice one for the response... only problem is I dont have a distributed application...its just daft, and only FT looks like it will fit the bill. I take it you mean limitations regarding CPU?

Given your response I have a couple of questions for you:

- I take it then I would need to run FT on the vMSC at a minumum after I have PP setup in the supported manner?
- oustide of FT, is there another product I could use that would get me to zero RTO, that you know of?

Roo

Look at the products called Zerto it will not give you RTO of 0 but you can get seconds.

I know what you mean about daft applications.

Yeah specifically I mean the limit of 1 vCPU. Generally speaking, an application that is important enough to genuinely require a zero RTO will need more than 1 CPU.

If you wanted to build it out on using a vMSC, then you would do:

Synchronous replication with merged FC fabric
Peer Persistence with Quorum Witness and Automated failover
VMware FT on top of that


that being said, here's the issue. The shadow VM will be in the other datacenter, and will have suboptimal paths to it's vmdk since the vmdk is mounted in datacenter A, but the shadow VM is in datacenter B. So depending on your intersite link, the performance of the VM could degrade (remember that VMware FT vm's are kept in lockstep).

The other issue is this: VMware FT does not help you one iota in cases of OS faults. So if your VM blue screens on one side, it's going to blue screen on the far end. If you are familiar with the two generals' problem, or byzantine failures, this can be an issue as well. The idea is that when things fail, they don't always fail nicely. Say your primary datacenter has a failure that results in it spewing corrupt data, then your issues there will translate to the backup site.

I have implemented a policy going forward that any application that is deemed "Mission Critical" in it's importance MUST be scalable and have application level HA. If it doesn't have it, we don't buy it.

nsnidanko, thanks.. I'll check it out...

Schmoog, you got any jobs going!!!?

Not at the moment heh.

Good luck with your app!

nsnidanko,

just a quick question, if you are familiar with Zerto... is the failover effectively a crash consistent (could be Application consistent from what I've read) reboot of the protected VM? so you'll effectively lose whatever was in memory on the protected VM upon failover?

Nice one
Roo

FYI: We tried cross site FT and it is too slow.
I'd wait for vSphere 6 before I'd even attempt this.

- Anders

Anders! excellent, thanks for joining this thread... I'm assuming you did so over 3par then?

Would you mind giving me some details around:
- what your latency was measuring from VM to VM?
- spec of dark fiber
- distance
- what method you stretched your fabric (FC, FCIP, FCoE...)

if you dont mind?

and I'd still be happy to hear any other solutions if someone can recommend them... zero RTO, is the key for now, until exhausted and customer gives the requirement up... I'm going to look into Zerto, but I have a feeling its just SRM beefed up and therefore involves a reboot upon failover.