Casey Bralla on 22 Sep 2010 02:54:15 -0700

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Re: [PLUG] Need Troubleshooting Advice: Disk Errors in Virtual Machines

On Wednesday 22 September 2010 12:51:22 am Lee Marzke wrote:
> On 09/21/2010 08:00 PM, Casey Bralla wrote:
> > On Tuesday 21 September 2010 7:25:26 pm Lee Marzke wrote:
> >> On 09/21/2010 06:04 PM, Casey Bralla wrote:
> >>> I've got a weird problem which I hope somebody here can help me figure
> >>> out.
> >>> 
> >>> I'm running about a dozen virtual machines (mostly web servers) on a
> >>> triple- core AMD system running Debian Lenny (ie: "Stable").  Each of
> >>> the virtual machines is also running Debian Lenny.
> >>> 
> >>> I am having repeated disk errors on the Virtual Machines, but no disk
> >>> errors on the host machine.  These disk errors often cause a Kernel
> >>> Panic within the VM, or otherwise crash the web server on the VM.
> >> 
> 64Mb per VM ?   That seems way, way too low.    The Debian
> recommendation is 256Mb + what is needed by apache.
> Is there some reason you have a dozen VM's ? Shouldn't apache handle
> hundreds of websites on a single VM ?
> Can I  assume you have thousands of websites then ?

Since these are solely used for Web Servers with VERY low traffic (~20 
hits/day), and I don't do any X-windows, it can actually run in 32 MBytes.   
The swap usage of the VMs seems minimal.

> If you really have that many VM's  you may need to re-think your
> architecture somewhat.   I don't think a
> single disk system with 4GB of RAM is going to run a dozen VM's,  that
> system is barely good for 4 servers
> servers.   CPU usually doesn't matter,  it's usually memory and then
> disk I/O that are the issue.      Here
> I have a dual socket dual-core Opteron 265 SuperMicro MB,  with 12GB
> RAM,  running ESXi 4.0

You are probably correct.  However, upgrading is a very remote possibility.  
These sites are donated to several family and friends.  I can't add RAM 
without spending $ hundreds, which the family budget won't allow.

Still, even if I were completely overloading the server, I would expect to see 
PERFORMANCE issues, not crashes.  In fact, performance seems pretty good.

I may have to change the architecture as you suggested and combine several 
sites on a single VM, but I was hoping to simplify (Ha!  That's working well, 
isn't it?!? <grin>) my setup by giving each customer and web page/blog a 
dedicated server.

I thought about switching to ESXi, but since BOTH VirtualBox & VMWare gave 
very similar problems, there must be some other underlying cause.  Also, ESXi 
seems like a $$ solution, which my CFO (Mrs Bralla) won't allow.

> I just gave a talk Monday at VMware user group on moving to ESXi [2],
> that you might find interesting.
> Lee
> [1]
> [2]
> n/presentation_view

Thanks for the suggestions!  I'll check out your presentation.


Casey Bralla
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