RE: [Xen-users] Looking for Xen success stories in a production data center environment

[Joe Armstrong <jarmstrong@xxxxxxxxxxxx>]

-----Original Message-----
From: Peter Booth [mailto:peter_booth@xxxxxxx] 
Sent: Monday, May 11, 2009 8:48 AM
To: Joe.Armstrong@xxxxxxxxx
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Looking for Xen success stories in a production data 
center environment

QqpI have real production data, some ppsitive, some negative. What is  
your context?

Are you talking about web app or batch?
Are you most concerned about throughput or respense time?
Are you concerned with self-managed or VPS/cloud environments?

The near-native observations you made don't tell the whole story. My  
experience is that most production applications are built and deployed  
in unoptimized states such that over-resourcing is the norm. A cost  
that's unique to virtualization is the erratic latencies due to  
hypervisor scheduling algorithm. In one example a rails app with  
consistent response times of 400ms native showed response times of  
400msec to 3sec virtualized, depending on %steal values. There are a  
couple of recent papers reporting similar data.

Sent from my iPhone
App
----

Hi Peter,

We are looking to run a linux-based mail server together with its web-based 
front-end, windows-based Active Directory server, and several other windows and 
linux-based products associated with the mail server.  The mail server will 
have lots of small file-based and network-based I/O and occasionally medium 
sized I/O depending on attachments.  Not dealing with streaming data or 
real-time responses.   This will be a self-managed environment (via a 
professional operations staff).

I have heard some hints of troubles if the number of VM's exceeds the number of 
cores - but internally we think we can manage that problem by not overloading a 
given physical platform.

I understand that we may have to give up some amount of performance for the 
better manageability & recoverability of a virtualized environment - that's OK. 
 Performance-wise I think we can tweak when needed and even run some components 
on physical hardware if needed.  Any insight you might have in that area would 
be greatly appreciated. 

As for stability, I have no idea... I have heard Xen is stable, but at this 
point I have no hard evidence of that - either for or against.  And I can't 
measure stability via some benchmark - that only comes from long-term running 
of a service.  I just don't know where to get that data.  Any clue on that ?

Thanks.

Joe

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