Below you find the next 3 answers which answer some of the questions posed in our "Ask the experts: Enterprise & Cloud computing" blog post.

Q ("Gamoniac"): Cloud is the buzzword, but while it makes sense to outsource hardware resources using cloud computing, does it really make sense to add extra layers of complexity to the application ?

A: Cloud computing does not necessarily add extra layers of complexity. Let me focus on the cloud computing that I know best: IaaS. Running a VM on for example Terremark's Enterprise Cloud is no different than running one on your own VMware based infrastructure. The only extra complexity comes from the fact that Terremark uses DRS (Dynamic Resource Scheduling). We have noticed that sometimes response times are relatively high even with medium traffic. This happens if your webtraffic has increased quickly the past minutes. The reason for these high response times is that DRS moves a previously low intensive website that has now become a lot more active to a different resource pool.

But that is about it. Our own measurements have shown that in most cases, using IaaS is not that different from running your own virtualized server.

While I have less experience with Amazon EC2, I believe the same applies. An Amazon VM runs after all on a Xen hypervisor. The real magic is the load balancing that goes on in the Amazon datacenter but that should be transparant to your application. Although I have to admit that it gets a lot more complex for storage intensive applications. It is lot harder to guarantee response times for those applictions.

Q ("Gamoniac"): Are the (cloud computing) savings justifiable to inadvertently creating a single point of failure?

One of the advantages of the better cloud vendors is that there is no single point of failure unless you have only one connection to the internet. As I explained in the previous post, it is unwise to rely on only one internet connection.

Large cloud vendors make sure that every link in the datacenter chain is redundant from power lines to redundant switches and storage (check out Google's Presentation here). It is very unlikely that the datacenter infrastructure of a typical SME can reach the same level of redundancy. 

Q ("FireKingdom"): Assume a server with 4 cpu's. Virtual Machine 1 (VM1) runs on cpu 1, VM2 runs on cpu 1, VM3 is on cpu 2. VM1 ask for data from VM2. VM2 ask its backup Vm3 to see if it has it. VM2 and 3 are like name servers. So they both trust each other and VM1 trust VM2 and VM3. Can VM3 send the data to VM1 with out leaving the machine and not involving the nic?

I'll assume that you run VMware's ESX as hypervisor. Then the answer is relatively simple: yes, if both VMs are connected to the same virtual switch. 

A VMware Virtual Switch (vSwitch) is a piece of software that is part of the kernel of ESX. So if your VMs are connected to the same vSwitch, the network traffic does not need to go on to the wire and will not be affected by the speed of the physical NIC. According to VMware's measurements, two Windows VMs at the same vSwitch can sent at a speed of about 1.35 to 1.6 Gbps to each other. Two Linux VMs were even capable of getting 2.5 Gbps. This was measured on ESX 3.5, vSphere and thus ESX 4.1 might even show better results.


 vSwitch is a network Layer Two device. So it cannot perform any routing.


If your VMs are on separate vSwitches, the traffic has to go through an external switch or even router (if the VMs are on a different network).



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  • brentpresley - Friday, July 29, 2011 - link

    So to answer the last question with a different twist, you should check out CA 3Tera AppLogic. It is a Xen and VMWare Dual HyperVisor Grid/Cloud OS that does interconnects between applications and VMs far far far better than VMWare has even been able to.

    To get an idea of what it can do, check out the video from CA here:
  • Sweeo - Saturday, July 30, 2011 - link

    No thank you
    About a week ago I had the misfortune for my router to die on me, so I think the "cloud" would not be a good idea for me for a start
    It took my isp 2 weeks to resolve the problem, even after I told them I knew what I was doing' and they use an encripted router, so anyother dint work >.<
    There is no way I would use the "cloud" for an other simple reason,security
    Aye as simple as that,the stuff igo on my computer is as safe as I can get it, but can you trust the "cloud"
    No thanks mate I stay here on terra firma
  • nnk - Sunday, July 31, 2011 - link

    Completely agree with your point of view. Cloud would be great 6 years ago, with even low-price PCs today having excess power for pretty much anything except gaming, it is just a corporate struggle thing.
  • Spivonious - Monday, August 1, 2011 - link

    Your ISP forces you to use their routers? Time to switch ISPs.
  • prophet001 - Monday, August 1, 2011 - link

    I agree 100%. Why should we offload our personal information to the corporations?

    Who better to trust with it than ourselves?

    The cloud to me looks like a big information grab along with some SaaS profits.
  • Ratman6161 - Tuesday, August 2, 2011 - link

    But I know plenty of people for whom a corporation would be more trustworthy about handling their personal information than they are themselves. I'm specifically talking about the several people I know who have the Ethernet cable from their cable modem plugged directly into their computer with nothing between them and the internet but false hope.

    I showed up at my in-laws house a couple of days after some cable guy had shown up at their house and "installed the internet" for them and found it set up just that way. My in-laws did not know any better and just knew that they could now browse the internet at high speed. I brought them an old router i had in my closet and did some basic configuration for them to at least keep them from being wide open to the world.

    So there are a lot of people out there where a cloud service could very well be more secure than their own system.
  • spikespiegal - Wednesday, August 3, 2011 - link

    Speaking from a corporate perspective I find it somewhat laughable that one of IT's biggest productivity headaches is users spending all day on FaceBook and Yahoo / Gmail, but when it comes to actually moving our business to the 'Cloud' our hackles suddenly go up.

    Corporate IT departments began to slim down in the early part of this decade, but the past few years have suddenly began to bloat again. Fat client desktop demand has stalled, and most of the time we spend running fixing smartphones which run better hooked to the 'net anyways.

    There isn't a CIO on this planet who'd rather spend his budget on development and productivity improvements rather than support a cluster of Exchange servers sucking up resources in the data center and requiring an additional Admin to dork around with PowerShell just to see how big mailboxes are (thank you Microsoft). So please, shove this garbage in the cloud and allow business to get back to business rather than every mid size Corp on the planet requiring an IT department.

    I agree that QoS is a huge issue and thanks to a unregulated environment the United States has a third world infrastructure in terms of net connectivity.
  • prophet001 - Thursday, August 4, 2011 - link

    The problem for me is that there is no "cloud." Behind every machine there's a face and a name. Albeit, one you don't know but the fact remains.

    Attempting to grant anonymity to the "cloud" by using words like "cloud" doesn't change the fact that you've made a decision to give someone you don't know and have never met significant access to your personal and/or business information.

    If you're OK with that then can you go ahead and give me your bank account number? While you're at it how about your social security number too? I am, after all, in the "cloud."

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