[Cialug] Guarantee SSH availability

[Kenneth Younger]

There's gotta be a book out there about this stuff that's pretty
comprehensive. Any suggestions?

On Tue, Jun 28, 2011 at 1:24 PM, Matthew Nuzum <newz at bearfruit.org> wrote:

>
> On Tue, Jun 28, 2011 at 12:06 PM, Kenneth Younger <kenny at sheerfocus.com>wrote:
>
>> I'm not sure what exactly occurred. It's a basic LAMP server with an nginx
>> proxy doing some caching there.
>>
>> Running this server has been humbling, because I used to think I knew what
>> I was doing with regard to running a server - but this thing has given me a
>> new respect for the subtle configuring that an expert can make.
>>
>> I know this isn't HUGE traffic, but it was getting 3000-4000 pageviews an
>> hour at peak, which is the most traffic I've ever seen on a site I run. I
>> think my problem is I just don't know how to tell what went wrong after the
>> fact...
>>
>> How would tell if it ran out of memory, or the CPU was just fully pegged,
>> or the disk started thrashing?
>>
>> -Kenny
>>
>>
> I know the feeling.
>
> PHP can be a bit harder to tune because the interpreter is part of Apache.
> Therefore it's hard to estimate how many child processes your system can
> support. If I was on a 512MB system I'd probably limit it to 20 and double
> that for a 1G or bigger system. If you find you've got a lot of spare memory
> under load then you can decide where to put it, often MySQL is a good
> candidate.
>
> I've seen situations like yours happen a few times in the last 18 months.
> In each case it was out of file handles. If that happens you're toast. You
> can't log in remotely to do anything about it.
>
> What I've done, and has paid off in spades, is run Xen to create my own VPS
> on a dedicated server. It means you need an extra IP address but it also
> means you've got a guaranteed bit of a safety net. You can ssh into your xen
> host (aka dom0) and then take over the console of your vm that's gone out of
> control and try to fix it or at least hold its hand in its final hour. It
> also means that a physical server can be divided up into smaller servers
> which might be convenient. LXC may be a good alternative if you aren't able
> to run Xen.
>
>
> --
> Matthew Nuzum
> newz2000 on freenode, skype, linkedin and twitter
>
> "Opportunity is missed by most people because it is dressed in overalls and
> looks like work." -Thomas Edison
>
>
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-- 
Kenneth Younger III
Founder, Sheer Focus Inc.
e: kenny at sheerfocus.com
p: (515) 367-0001
t: @kenny <http://twitter.com/kenny>
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