Comment by irahul | Hacker News Reader

Comment by irahul | Hacker News Reader

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Yahoo uses a similar setup. Instead of virtual hosts, the hosts here are physical machines. Search team had a dedicated lab(not sure what's happening now with search migration) and all developers would ssh to their assigned lab machines, fire up their vim/emacs and crank code.

Search team has a mixture of windows laptops, macs, linux desktops, linux laptops..and it didn't matter because everyone just ssh'd to a RHEL box and worked.

Yahoo used to be a BSD shop, then moved to linux. Search team used both Debian and RHEL in the beginning, then transitioned to RHEL fulltime.

I don't understand the obsession with RHEL. In my experience, Debian/Ubuntu will give the same benefits as RHEL sans the cost.

The rationale for moving from BSD to linux was practical. The gist was most of the vendors either do not do bsd or bsd was second class citizen. And BSD wasn't as quick as linux in catching up with esoteric hardware. But discarding Debian didn't actually make sense to me.

Yahoo used to be a BSD shop, then moved to linux.

Yahoo still uses BSD. They're not completely BSD, of course; but they're not completely linux either.

Yep.Yahoo still uses BSD, but earlier, a lot of work was put on BSD. There were BSD kernel teams, and teams which managed BSD ports. AFAIK, almost all of the new development is on RHEL and there aren't any BSD dedicated teams now. A lot of BSDs are still around - some have been running for last 10 years or so.

Some new teams use BSD for their webapp deployment and database servers; can't confirm (no links) but I think the teams were of the opinion MySQL on BSD was more stable.

But as said, earlier Yahoo was big time BSD, investing in it and submitting patches, which no longer is the case. Search team did a mass migration to RHEL about 2 years back. BSD is still used here and there as deployment platform. My personal preference would be to go with BSD and save some buck but apparently management views it differently.

I've been a FreeBSD developer since 2003 and I'm on the FreeBSD core team. I know the history of Yahoo and FreeBSD. ;-)

I knew about your FreeBSD background. Didn't know you were involved with Yahoo dealings though.

CERN used RH too, 6 when I was there. I believe they've now switched to Scientific Linux.

Actually I don't understand why Google would use virtualisation. Why would they split a physical box up? Making many hosts look like one, yes (is such a thing possible?), but not the other way around.

And AFS was cool: it was actually a global filesystem that many institutions used. you could cd /, ls and browse to nasa.gov amongst many thousands of others (much was protected!) (cern was mounted on /cern.ch)

I don't understand why Google would use virtualisation. Why would they split a physical box up?

Ease of administration. It turns out to be much easier to have ten virtual machines running one daemon each than one virtual machine running ten daemons. Fewer interactions, cleaner process boundaries (the boundary between one VM and another is pretty thick), easier debugging. Easier to swap out parts without affecting other parts. Much easier scaling. (If you need more servers for Service X, launch more VMs; if your machine needs more RAM to hold those VMs, launch the VMs on a different physical box -- the system doesn't need to be changed to support that because it's already architected to assume separate "machines" for everything.)

For more on the subject ask Ezra Zygmuntowicz or his blog and books. I stole all of this material from him.

It turns out to be much easier to have ten virtual machines running one daemon each

It's funny, when you needed one OS instance per network server daemon on Windows in the 90s, everyone laughed at it. Now it counts as cutting edge thought.

Everyone laughed at it because at the same time there were OSes available that could run unlimited number of daemons simultaneously.

Now it's a matter of choice for system owner. And of course all those single-daemon VMs run inside OS that lets numerous VMs run at the same time.

Not to mention that you can do cool things with virtual machines like live migration and fail-over from one physical machine to another in a fully transparent way.

Would Solaris containers or Linux VServer work as well here? One would need good management tools, of course.

I haven't gotten super in depth with containers (zones or ldoms) but I don't think they inherently offer nearly as much flexibility as vmware.

Not to mention Solaris 10 can be...interesting.

that's a great response, cheers

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