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Joined 8 months ago
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Cake day: November 15th, 2023

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  • No, it’s not true. A single system has less failure scenarios, because it doesn’t depend on external controllers or anything that makes the system distributed and that can fail causing a failure to your system (which may or may not be tolerated).

    This is especially true from a security standpoint: complexity adds attack surface.

    Simple example: a kubernetes cluster has more failure scenarios than a single node. With the node you have hardware failure, misconfiguration of the node, network failure. With a kubernetes cluster you have all that for each node (each with marginally less impact, potentially, because it depends for example on stateful storage, that if you mitigate you are introducing other failure scenarios as well), plus the fact that if the control plane goes in flames your node is useless, if the etcd data corrupts your node is useless, anything that happens with resources (a bug, a misuse of the API, etc.) can break your product. You have more failure scenarios because your product to run is dependent on more components to work at the same time. This is what it means that complexity brings fragility. Looking from the security side: an instance can be accessed only from SSH, if you are worried about compromise you have essentially one service to secure. Once you run on kubernetes you have the CI/CD system, the kubernetes API, the kubernetes supply-chain, etcd, and if you are in cloud you have plenty of cloud permissions that can indirectly grant you access to the control plane and to a console. Now you need to secure 5-6-7 entrypoints to a node.

    Mind you, I am not advocating against the use of complex systems, sometimes they are necessary, but if the complexity is not fully managed and addressed, you have a more fragile system. Essentially complexity is a necessary evil to respond to some other necessities.

    This is the reason why nobody would recommend to someone who needs to run a single static website to run it on Kubernetes, for example.

    You say “a well designed system”, but designing well is harder the more complexity exists, obviously. Redundancy doesn’t always work, because redundancy needs coordination, needs processes that also depend on external components.

    In any case, I agree that you can build a robust system within Cloud! The argument I am trying to make is that:

    • you need to be aware that you are introducing complexity that needs attention and careful design if you don’t want it to result in more fragility and exposure
    • you need to spend way more money
    • you need to balance the cost with the actual benefits you are gaining

    And mind you, everything you can do in Cloud you can also do on your own, if you invest on it.


  • If your compute needs expand that much everyday, and possibly shrink in others, than your use-case is one that can benefit from Cloud (I covered this in the post).

    That said, if provisioning means recycle, then it’s obviously not a problem.

    This is a very rare requirement. Most companies’ load is fairly stable and relatively predictable, which means that with a proper capacity planning, increasing compute resources is something that happens rarely too. So rarely that even a lead time for hardware is acceptable.

    So if I may ask (and you can tell), what is the purpose of provisioning that many systems each day? Are they continuously expanding?




  • Of course the problem is solved, but that doesn’t mean that the solution is easy. Also, distributed protocols still need to work on top of a complicated network and with real-life constraints in terms of performances (to list a few). A bug, misconfiguration, oversight and you have a problem.

    Just to make an example, I remember a Kafka cluster with 5 replicas completely shitting its pants for 6h to rebalance data during a planned maintenance where one node was brought offline. It caused one of the longest outages to date with the websites which relied on it offline. Was it our fault? Was it a misconfiguration? A bug? It doesn’t matter, it’s a complex system which was implemented and probably something was missed.

    Technology is implemented by people, complexity increased the chances of mistakes, not sure this can be argued.

    Making it harder to identify SPOF means you might miss your SPOF, and that means having liabilities, and having anyway scenarios where your system can crash, in addition for paying quite a lot to build a resilience that you don’t achieve.

    A single instance with 2 failure scenarios (disk failure and network failure) - to make an example - is not more fragile than a distributed system with 20 failure scenarios. Failure scenarios and SPOF can have compensating controls and be mitigated successfully. A complex system where these can’t be fully identified can’t have compensating control and residual risk might be much harder. So yes, a single disk can fail more likely than 3 disks at once, but this doesn’t give the whole picture.



  • I wish it worked like that, but I donct think it does. Connecting clouds means introducing many complex problems. Data synchronization and avoiding split-brain scenarios, a network setup way more complex, stateful storage that needs to take into account all the quirks and peculiarities of all services across all clouds, service accounts and permissions that need to be granted and segregated for all of them, and way more. You may gain resilience in some areas, but you introduce a lot more things that can fail, be misconfigured or compromised.

    Plus, a complex setup makes it harder by definition to identify SPOFs, especially considering it’s very likely nobody in the workforce is going to be an expert in all the clouds in use.

    To keep using your simile of the disks, a single disk with a backup might be a better solution for many people, considering you otherwise might need a RAID controller that can fail and all the knowledge to handle and manage a RAID array properly, in addition to paying 4 or 5 times the storage. Obviously this is just to make a point, I don’t actually think that RAID 5 vs JBOD introduces comparable complexity compared to what multi-cloud architecture does to single-cloud.








  • Is that what you get with Cloud? Because there are still a million ways to shoot yourself in the foot. The main difference is that the single genius doesn’t need to implement things him/herself, but decisions still need to be taken and fragile setups can still be built.

    Imagine an ec2 instance in a satellite account performing some business critical function with an instance role, whose custom IAM policy allows to do it in another account. Clouds are not giving you good engineering, they are giving you premade building blocks, you can absolutely still make a mess with those. Even more, the complexity and the immense portfolio of features can allow very creative ways to build very low-quality systems.

    I think you can have good, boring, simple systems built by engineers. With or without Cloud services.




  • Thanks!

    But I have to think the massive costs of cloud junk also pay a role in stuff like a calendar charging double digit annual fees for something that takes very little storage and very little computation (and you of course can’t just buy software any more).

    Absolutely agree. I did not even think about this aspect, but I think you are absolutely spot on. Building something with huge costs is something that ultimately gets passed to the users in addition to the rent-seeking aspect.

    I have no words for multi-cloud.

    You and me both. I have to work with it and the reality is, there is nobody who actually understands the whole thing. The level of complexity (and fragility, I might add) of it all is astonishing. And all of this to mitigate some (honestly) low risk of downtime from the cloud provider. I have lobbied a little bit against at work, but ultimately it has become a marketing tool to sell to customers, so goodbye any hope of rational evaluation…