5 ms·

Can the majority of webapps run on a single machine? Probably. Do most of your customers expect close to 100% uptime? Yes. Does one machine provide the uptime

Can the majority of webapps run on a single machine? Probably. Do most of your customers expect close to 100% uptime? Yes. Does one machine provide the uptime required by your customers? Most definitely not.

userbinator 3y ago
Make it two machines then.
- master_crab 3y ago
  Ya. 1<n<6 has worked 99% of the time for me.
Jgrubb 3y ago
The correct answer to question 3 is "it depends".
sjducb 3y ago
Master slave failover will give you less than a second of downtime.
- hparadiz 3y ago
  Pretty much any provisioned vm can be split down the middle. Got 4 cpus and 4gb of ram? Congrats you have two vms with 2 cpus and 2gb of ram. Throw them into a 50/50 load balancer and never have any downtime.
  - toast0 3y ago
    Two vms on the same machine doesn't help when the machine fails. Also, I sure hope your loadbalancers don't suck. I've worked with some that had worse uptime than my servers, and worse capacity too. Went back to putting the two host addresses in DNS, which is mostly fine, but means a lot of waiting when you want to take a host out of rotation for disruptive maintenance.
    - hparadiz 3y ago
      I do this on AWS so the load balancer is managed for me. Never had issues. Two randomly provisioned vms are unlikely to be on the same bare metal.
      - aflukasz 3y ago
        You do have some control (quite typically?): https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placemen..., https://docs.hetzner.com/cloud/placement-groups/overview https://docs.hetzner.com/cloud/placement-groups/overview.
  - viraptor 3y ago
    VMs going down is not an unexpected event. It's not going to happen even day, but hosts crash, network goes down, datacentres experience thermal events, etc. Your solution may work for your own system crashes, but not most of the rented platform failure modes.
Puts 3y ago
Well if you can spin up a new environment in less than a minute – does it matter? I mean if you are Facebook yes, but having worked with a lot of people building things like web shops – having a minute downtime I would say is fine because I've seen so many of these people shoot themself in the foot trying to build high-availability solutions and having constant downtimes just because they can't handle their own complexity.
- ardel95 3y ago
  If you have the ability to spin up a new machine when the old one fails, and deploy your app onto it in one minute, it’s not a big leap to also run your app on two machines and avoid that downtime altogether.
  - Nextgrid 3y ago
    Running two instances of a stateful application in parallel forces you to consider nasty and hard problems such as CAP theorem, etc. If your requirements allow, it's much easier to have an active-standby architecture over active-active.
    - ardel95 3y ago
      Totally. But most applications are not stateful.
      - echoangle 3y ago
        Is it really an application if it’s not stateful? Maybe you’re managing the state client-side which makes it easier but I wouldn’t call a plain website an application, or am I missing something?
        Nextgrid 3y ago
        At the smallest level, even every byte of an in-flight HTTP request is still state. State, and for that matter "uptime" really depend on what the application/service ultimately does and what the agreement/SLA with the end-customer is. The correct high-availability solution should take business requirements into account and there is no silver bullet. Running everything on a $5 VPS is no silver bullet, but neither is your typical "cloud-native" "best practice" stack that everyone keeps cargo-culting which often leads to unnecessary cost while leaving many hard questions (such as replicating CAP-bound stateful databases) unanswered.
fabian2k 3y ago
I don't think the point here changes all that much if you change this to two servers and a load balancer. That's still a pretty simple setup. But I also think that many applications are far more tolerant of small outages than you imply. And a more complex setup also adds more points that can lead to an outage even though it reduces the chance that hardware will cause one.
- kasey_junk 3y ago
  Nearly no one is competent and able to setup a true load balancer. If you have one either it’s provided by your (most likely vm based) hosting provider or you are a big enterprise. If you are in one of those two categories then setting up something more robust than a single server isn’t much more complicated than a single server. That is to say, I think it very much does change the equation around the original statement.
- Aachen 3y ago
  Wouldn't you also need two load balancers then? Otherwise you've still got a single point of failure. And how do you keep the failover system in sync? It's a whole can of worms to promise 100% uptime. It's super rare that a server physically breaks and suddenly goes dark with less than a day's warning, and for most applications such a once-in-5-years event is tolerable if that means the hosting costs are divided by five as well (so far I'm ~10 years in and haven't experienced such an event yet; disks in RAID have broken but not a cpu or other SPOF)
  - erik_seaberg 3y ago
    > super rare that a server physically breaks I kinda want to know where you shop, because commodity hardware has a reputation as just utter crap. Before cloud went mainstream, I worked somewhere that had some racked servers in a colo literally catch fire. (The remote hands put them out, disconnected, and refused to touch them ever again.)
ocdtrekkie 3y ago
You'd be surprised how close to 100% uptime you can get on one machine with well-engineered software. Schedule an automated update and reboot for a time and day of the week you have the fewest customers monthly, and if you have an SSD as the boot drive, unless you are a huge company nobody will notice or care that at 4 AM on Sunday your service was down for a minute and a half.
- NorwegianDude 3y ago
  You can also avoid most reboots by livepatching the kernel.
  - ocdtrekkie 3y ago
    Indeed. I come from the Windows world where things are a lot slower and there are less options for things like livepatching. So my "minute and a half downtime" is definitely pessimistic compared to what you can accomplish on a Linux server.
maxcoder4 3y ago
>Do most of your customers expect close to 100% uptime? Yes. I think this is mostly a self imposed requirement. Banks regularly have overnight technical breaks. My country national rail has 30 minutes of downtime every night (!). Unless your product is already global, most people won't have a problem with occasional overnight scheduled downtime.
- Solvency 3y ago
  Banks have most people by the balls. Most SaaS don't and wish they did.
SkyPuncher 3y ago
You’d be surprised. Most people never even test number 2. If your a novel or niche product, you can afford a “lot” of downtime For number 3, it really all depend on your load. I’ve run most early stage startups on an incredibly simple setup with a proxy placed in front of an app server. Occasionally, our monitoring will start reporting high p99’s so we go in and bump the servers to the next tier or scale horizontally just a bit more. Eventually, that breaks down but many startups will be well into Series A or Series B point. At that point, you know your customer’s needs and can hire dedicated engineers to solve reliability and uptime.
nektro 3y ago
how many websites out there realistically need close to 100% uptime?
watermelon0 3y ago
Multiple machines don't automatically mean a better uptime. Outside of the regular maintenance, many problems can affect multiple instances, not just one. (Regular maintenance meaning OS updates needing a reboot, which happens like what? Once per month for a minute?)
NorwegianDude 3y ago
Servers are a lot more stable than you think.

userbinator 3y ago

Make it two machines then.

master_crab 3y ago
Ya. 1<n<6 has worked 99% of the time for me.

Jgrubb 3y ago

The correct answer to question 3 is "it depends".

sjducb 3y ago

Master slave failover will give you less than a second of downtime.

hparadiz 3y ago
Pretty much any provisioned vm can be split down the middle. Got 4 cpus and 4gb of ram? Congrats you have two vms with 2 cpus and 2gb of ram. Throw them into a 50/50 load balancer and never have any downtime.
- toast0 3y ago
  Two vms on the same machine doesn't help when the machine fails. Also, I sure hope your loadbalancers don't suck. I've worked with some that had worse uptime than my servers, and worse capacity too. Went back to putting the two host addresses in DNS, which is mostly fine, but means a lot of waiting when you want to take a host out of rotation for disruptive maintenance.
  - hparadiz 3y ago
    I do this on AWS so the load balancer is managed for me. Never had issues. Two randomly provisioned vms are unlikely to be on the same bare metal.
    - aflukasz 3y ago
      You do have some control (quite typically?): https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placemen..., https://docs.hetzner.com/cloud/placement-groups/overview https://docs.hetzner.com/cloud/placement-groups/overview.
- viraptor 3y ago
  VMs going down is not an unexpected event. It's not going to happen even day, but hosts crash, network goes down, datacentres experience thermal events, etc. Your solution may work for your own system crashes, but not most of the rented platform failure modes.

Puts 3y ago

Well if you can spin up a new environment in less than a minute – does it matter? I mean if you are Facebook yes, but having worked with a lot of people building things like web shops – having a minute downtime I would say is fine because I've seen so many of these people shoot themself in the foot trying to build high-availability solutions and having constant downtimes just because they can't handle their own complexity.

ardel95 3y ago
If you have the ability to spin up a new machine when the old one fails, and deploy your app onto it in one minute, it’s not a big leap to also run your app on two machines and avoid that downtime altogether.
- Nextgrid 3y ago
  Running two instances of a stateful application in parallel forces you to consider nasty and hard problems such as CAP theorem, etc. If your requirements allow, it's much easier to have an active-standby architecture over active-active.
  - ardel95 3y ago
    Totally. But most applications are not stateful.
    - echoangle 3y ago
      Is it really an application if it’s not stateful? Maybe you’re managing the state client-side which makes it easier but I wouldn’t call a plain website an application, or am I missing something?
      - Nextgrid 3y ago
        At the smallest level, even every byte of an in-flight HTTP request is still state. State, and for that matter "uptime" really depend on what the application/service ultimately does and what the agreement/SLA with the end-customer is. The correct high-availability solution should take business requirements into account and there is no silver bullet. Running everything on a $5 VPS is no silver bullet, but neither is your typical "cloud-native" "best practice" stack that everyone keeps cargo-culting which often leads to unnecessary cost while leaving many hard questions (such as replicating CAP-bound stateful databases) unanswered.

fabian2k 3y ago

I don't think the point here changes all that much if you change this to two servers and a load balancer. That's still a pretty simple setup. But I also think that many applications are far more tolerant of small outages than you imply. And a more complex setup also adds more points that can lead to an outage even though it reduces the chance that hardware will cause one.

kasey_junk 3y ago
Nearly no one is competent and able to setup a true load balancer. If you have one either it’s provided by your (most likely vm based) hosting provider or you are a big enterprise. If you are in one of those two categories then setting up something more robust than a single server isn’t much more complicated than a single server. That is to say, I think it very much does change the equation around the original statement.
Aachen 3y ago
Wouldn't you also need two load balancers then? Otherwise you've still got a single point of failure. And how do you keep the failover system in sync? It's a whole can of worms to promise 100% uptime. It's super rare that a server physically breaks and suddenly goes dark with less than a day's warning, and for most applications such a once-in-5-years event is tolerable if that means the hosting costs are divided by five as well (so far I'm ~10 years in and haven't experienced such an event yet; disks in RAID have broken but not a cpu or other SPOF)
- erik_seaberg 3y ago
  > super rare that a server physically breaks I kinda want to know where you shop, because commodity hardware has a reputation as just utter crap. Before cloud went mainstream, I worked somewhere that had some racked servers in a colo literally catch fire. (The remote hands put them out, disconnected, and refused to touch them ever again.)

ocdtrekkie 3y ago

You'd be surprised how close to 100% uptime you can get on one machine with well-engineered software. Schedule an automated update and reboot for a time and day of the week you have the fewest customers monthly, and if you have an SSD as the boot drive, unless you are a huge company nobody will notice or care that at 4 AM on Sunday your service was down for a minute and a half.

NorwegianDude 3y ago
You can also avoid most reboots by livepatching the kernel.
- ocdtrekkie 3y ago
  Indeed. I come from the Windows world where things are a lot slower and there are less options for things like livepatching. So my "minute and a half downtime" is definitely pessimistic compared to what you can accomplish on a Linux server.

maxcoder4 3y ago

>Do most of your customers expect close to 100% uptime? Yes. I think this is mostly a self imposed requirement. Banks regularly have overnight technical breaks. My country national rail has 30 minutes of downtime every night (!). Unless your product is already global, most people won't have a problem with occasional overnight scheduled downtime.

Solvency 3y ago
Banks have most people by the balls. Most SaaS don't and wish they did.

SkyPuncher 3y ago

You’d be surprised. Most people never even test number 2. If your a novel or niche product, you can afford a “lot” of downtime For number 3, it really all depend on your load. I’ve run most early stage startups on an incredibly simple setup with a proxy placed in front of an app server. Occasionally, our monitoring will start reporting high p99’s so we go in and bump the servers to the next tier or scale horizontally just a bit more. Eventually, that breaks down but many startups will be well into Series A or Series B point. At that point, you know your customer’s needs and can hire dedicated engineers to solve reliability and uptime.

nektro 3y ago

how many websites out there realistically need close to 100% uptime?

watermelon0 3y ago

Multiple machines don't automatically mean a better uptime. Outside of the regular maintenance, many problems can affect multiple instances, not just one. (Regular maintenance meaning OS updates needing a reboot, which happens like what? Once per month for a minute?)

NorwegianDude 3y ago

Servers are a lot more stable than you think.