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I've been asked to do this as a presentation, but to be honest, either I've totally missed the point or am I being asked to compare an actual company i.e. Stratus against the concept of virtualising machines, in regards to high availability solutions?

Having done some research I know that Stratus are a supplier of FT and HA services, in both hardware and software, and that virtualisation can be used as a HA solution, but how can you compare a company vs an concept/idea?

Or have I totally missed the boat here?

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closed as not a real question by Dave M, HopelessN00b, gWaldo, rnxrx, Chris McKeown Sep 10 '12 at 22:47

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

2 Answers 2

I agree with you - these are not discrete concepts. Stratus is a supplier of services and hardware, some of which include virtualisation too.

May I be as bold as to suggest that whoever set you this task doesn't really understand? Does it have to be a "vs" presentation? Maybe you could take the time to explain the fundamental concepts of virtualisation, high availability, fault tolerance and some of the ways that these can be achieved.

I'd let Stratus do the sales spiel themselves, personally.

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It's for a final stage job interview, the topic as set by the head of IT, so I'm thinking this is either a typo, or they've purposely set the topic like this to see how I will perform, as I said, I don't see how they can be compared easily? –  thexhangman Sep 6 '12 at 16:22
@thexhangman And after receiving this question, what possible reason do you have for still wanting the job? ~"Thanks for your interest, but I don't work for asshats. On a related topic, are you accepting applications for the position of 'head of IT'?" –  HopelessN00b Sep 6 '12 at 16:45
@HopelessN00b I don't see what's wrong with a boss that knows less than you about your job and is willing to admit it by asking questions like this. Much better than the ones that bluff and bluster and tell you "we need to be virtual so I ordered a VMWare Stratus HyperV and had them paint it mauve because I heard those have more RAM". I know less about the managerial stuff my boss has to do than he does. He knows less about the technical stuff than I do. He's being paid to be a dept. manager, I'm being paid to be the technical manager. Where's the problem? –  RobM Sep 6 '12 at 19:12
@DJPon3 Other than the staggering level of WTF the question demonstrates, is a functional environment really going to be putting this foot forward and or screening potential recruits based on such a mishmash of buzzwords? I think not. –  HopelessN00b Sep 6 '12 at 19:45
Maybe. Maybe not. What if, as has been already suggested, they're clueful enough to understand this and ask a broken question on purpose, just to see what kind of answer they get? –  RobM Sep 6 '12 at 19:58

Let's consider "Stratus" as a proxy for both Fault Tolerance and High Availability, supplied in both hardware and software. Assume, for the moment, that they are not the only such vendor.

Whole-machine virtualization, as opposed to things like a Java VM, separates software state from hardware state, by wrapping up an operating system and all the applications running on top of it into a neat container. Once you have that container, it becomes easier to accomplish things like HA and FT. Hardware-layer and hardware/software-layer HA and FT solutions like you traditionally bought from Stratus accomplish the same thing, but without as strong a separation between hardware and software. Keep in mind, however, that there's a fairly murky boundary between these things, that's becoming murkier all the time, as Stratus and others move toward virtualization techniques to accomplish those things that used to be done entirely with hardware.

Pretty much all the major virtualization packages can give you HA. This is accomplished by storing the virtual machine files (both configuration and disk images) on something that all members of a host cluster can access. This might be a file server or a SAN, or something somewhere in between. If something goes catastrophically wrong with the physical machine hosting your VM, another member of the cluster picks up that VM and runs it. The guest OS sees a crash and reboot. It's offline for not much longer than it takes the OS to boot. If a problem is not catastrophic, you can move the running VM (called Live Migration or vMotion) to another host and avoid the problem.

Actual Fault Tolerance is a little slipperier. You have to decide what it means to you. If it means that you tolerate a single network cable being kicked out by a maintenance person, then you can get that through NIC teaming. If it means that you tolerate a single power supply failure, you might buy a machine with redundant power supplies. If it means that a catastrophic failure of a host doesn't take the workload offline, as many people interpret it, then only a couple of hypervisors can currently give you that, and the ones that can will do so at a fairly high cost in terms of performance. They work either by running the VM in two places at the same time in lock step, or by taking thousands of snapshots of the VM per second and shipping them to another host, waiting as a standby.

Hardware is generally faster, but much more expensive.

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