
The Stack Exchange Architecture - javery
http://blog.serverfault.com/post/the-stack-exchange-architecture-2011-edition-episode-1/
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barranger
Interesting to see one of these Architecture blog posts for a site running on
the .Net framework.

Does 9.5-10 Million hits a day make them the largest .Net backed site?

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smoyer
Windows + Ubuntu + CentOS ... I'm curious to know how the OS selection was
made and specifically why the HAProxy servers are Ubuntu and the Redis servers
are CentOS. Do your admins work on all three OSs?

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gbeech
It's pretty simple, we started off on Ubuntu for our linux boxes. Then made a
decision to move to CentOS for the stability and vendor package compatibility
for our core services. However, We are going to stick with Ubuntu on some of
our back end servers - management and utility servers for the larger package
repositories. Our Core Q&A engine is written in C# with MS-SQL databases so
obviously we need to run windows for that.

There are only 2 sysadmins so yes we work on all OS's

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thwarted
Any good Linux admin should be able to work on any distribution... and will...
as long as you allow them to complain about it.

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mikerg87
I found it curious that there is so much hardware that is at around 20%
utilization. Wouldn't it be better to have less hardware with higher
utilization and buy cheaper/better hardware later if warranted?

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biot
Time for the sysadmin math quiz:

10 servers running at 20% utilization. Two servers experience hardware
failure. What's the resulting utilization per server?

4 servers running at 50% utilization. Two servers experience hardware failure.
What's the resulting utilization per server?

Which approach affords greater redundancy and room for growth?

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jodrellblank
R610s are going to have dual PSUs, and they have redundant storage
arrangements, so potentially they could experience hardware failure but no
downtime.

Chance of hardware failure in a modern server in a colo, assuming it's been
stress tested to find DOA hardware before being put in production? Low.

A quick spec on Dell's site, rough guess for the SSDs, the web servers are
running around $4,000 each, or $4,500 with better warranty. Saving of 6
servers is >$20,000.

It's entirely up to their funding and growth plans and risk acceptance if
that's a useful saving, but if they were a ramen-profitable-is-goal-one
startup, it would be months of runway.

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biot
They apparently have two developer/sysadmins, so the $20K savings is less than
a month of their salaries. For the redundancy and growth that affords, it's a
no-brainer.

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Goladus
Do you have additional datacenter environments for staging and development?

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fleaflicker
From the end of the post:

 _We backup our databases nightly and restore them to two different locations.
One local to our NY data center for our devs to work against, and one remote
in our OR data center._

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brunnsbe
This is a nice overview. The article mentions database pairs for the MSSQL
servers. What high availability mode is used, database mirroring or cluster?

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xtacy
Could someone clarify this: the post says that the servers are in _our_ Data
Center in NY and OR. I have always thought that DCs host 100s to 100,000
machines! Is this a colo?

EDIT: What is the typical network utilization for such web-services?

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gbeech
yes, we are in two colo's one in Oregon and one in NYC

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DodgyEggplant
everything: DB, Web servers etc aprox 600GB RAM

