Comment by feld | Hacker News Reader

Comment by feld | Hacker News Reader

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> They are already dumping Solaris/AIX/HP-UX as much as they can so environments are a bit more homogeneous (and easier to support).

Whoever is pushing for this is an idiot then. Verisign, for example, has had 100% DNS uptime for the .net, .org, and .com root servers for ~15 years because of their mixed environments. In every one of their POPs they tend to have at least two racks of equipment with:

   * 2 different brands of load balancers
   * 2 different brands of firewalls
   * 2 different brands of switches
   * 2 different brands of servers
    ** servers are from different hardware generations
   * 2 different OSes (Linux and FreeBSD)
   * a choice from 3 different DNS server software

This is all pretty much randomized at each location. As a result, a bug in one piece of the stack (hardware, software, driver, security, etc) will not take down their service completely.

This is how you run a reliable global-scale service. Anyone who plays the "it's just easier if we all use ____" is in for a big surprise when their entire infrastructure is at risk due to one bug.

Yet Google and Facebook keep using Linux for all their servers.

Facebook also uses PHP, the most reviled language around here. Google has a developer team to rewrite components and adapt the Linux kernel, consider that.

I don't recall seeing Facebook or Google have 15 years of uninterrupted service.

It's an unfair comparison in any case: DNS is "trivial" to keep up compared to even small fractions of Facebook and Google's infrastructure.

As long as a sufficient fraction of servers at a sufficient fraction of Verisigns clusters has an uncorrupted set of data and is able to serve responses, Verisigns TLD zones remain up.

Pretty much the only thing that can go wrong in that case, assuming you have safeguarded the integrity of the zone is bugs in components outside their direct control.

It makes 100% sense for them to focus their efforts on ensuring diversity, because the class of problems that can solve for them makes up an unusually high percentage of the possible failure classes, and the nature of the service also means that most of the potential problems that this can cause is only likely to take out some proportion of their capacity that still leaves them with a functional system, so the potential benefit is higher for them than for most with a heterogeneous, and the potential risks are lower for them than for most.

For Google and Facebook, the systems are so much more complex that the tradeoffs are vastly different.

It's equally trivial if you serve your web infrastructure off of load balanced caches.

Sort of (ignoring that web browsers don't retry failed requests), if all you are serving is static/cacheable content.

Which excludes the vast majority of functionality of Google/Facebook, and most other major web properties.

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