OpenVZ versus Xen or others


#1

Hi again. All the great assistance so far has moved me along. I’m
still a Linux noob but I’ve settled on CentOS 4.4 and have it up and
running on a test server right now. I’ll be testing two scenarios: one
with Apache 2.2 and mod_proxy_balancer in front of a mongrel cluster,
and another with NGINX in front of a mongrel cluster.

Remeber I have 3 machines with dual, dual-core Xeons and 16gb of ram per
server and I want to maximize the performance, 146gb of storage on two
and a 73gb mirror with a 600gb raid 5 on the last one (I had intended to
use the raid5 for the mySQL database). So I’ve looked into
virtualization a bit to see what the benefits might be and it sounds
great. Now I noticed that XenExpress only supports up to 4gb of ram and
I understand there may be a mySQL 4gb per process limit as well. I
could buy commercial Xen but I found OpenVZ (open source branch of
Virtuozzo) and it sounds pretty good too. I understand that each
solution accomplishes virtualization in different ways though so any
guidance would be appreciated.

Also, my initial quess is that I should be able to put about 2 or 3
virtual servers on each machine, including the database server and have
the two webservers being fed by a hardware load balancer and accessing
the 3rd server for mySQL data.

Again, thanks for any guidance!

Raul


#2

Raul wrote:

virtualization a bit to see what the benefits might be and it sounds
great. Now I noticed that XenExpress only supports up to 4gb of ram and
I understand there may be a mySQL 4gb per process limit as well. I
could buy commercial Xen but I found OpenVZ (open source branch of
Virtuozzo) and it sounds pretty good too. I understand that each
solution accomplishes virtualization in different ways though so any
guidance would be appreciated.

We’ve been testing both of these solutions out. Xen is pretty rocking if
you want to manage several different distros and such. Each virtual
server has it’s own kernel running with Xen… which will take more
resources on the server than OpenVZ. There is also the overhead of
managing that many more servers/kernels.

OpenVZ shares it’s kernel with each of the virtual machines and works
more like a FreeBSD jail. One of the cool features that really caught
our attention as we’ve been investigating tools for our new product is
live migrations!

“Delivery of the checkpointing and live migration functionality as part
of OpenVZ brings a capability that no other open source operating
system-level virtualization software offers. It allows system
administrators to move virtual servers between physical servers without
end-user disruption or the need for costly storage capacity.”

http://openvz.org/news/announcements/kernel-2.6.9-stable-20061114

…pretty cool, huh?

-Robby


Robby R.
http://www.robbyonrails.com/


#3

On Feb 8, 2007, at 7:30 PM, Robby R. wrote:

ram per
Virtuozzo) and it sounds pretty good too. I understand that each
OpenVZ shares it’s kernel with each of the virtual machines and works
end-user disruption or the need for costly storage capacity."

http://openvz.org/news/announcements/kernel-2.6.9-stable-20061114

Ummm… Xen can do this too.

…pretty cool, huh?

definitely cool, to be able to move a whole VM from one host to
another without any down time is kick ass :wink:

-Robby


Robby R.
http://www.robbyonrails.com/
http://www.planetargon.com/

Xen outperforms openvz. It also doesn’t allow the host to oversell
boxes. OpenVZ allows physical resource to be oversold based on the
premis that hopefully not all of the VM’s go nuts with cpu and mem at
the same time.

If this is your own 3 servers and you have lots of ram then I think
Xen is the better choice. You do pay for running a kernel for each
VM but you gain better isolation and performance for this.

Cheers-
– Ezra Z.
– Lead Rails Evangelist
– removed_email_address@domain.invalid
– Engine Y., Serious Rails Hosting
– (866) 518-YARD (9273)


#4

I’ve had experience with both OpenVZ and Xen on with different hosting
companies. The OpenVZ server we had with vpslink.com just would not
install Oracle XE. It was a problem with swap memory. The VPS at
vsplink didn’t have any, and even though it had plenty of memory
Oracle would just crap out during install. I’m not sure if this is
related to some limitation with OpenVZ, but most Xen hosts I’ve seen
give you some swap, too. I even tried enabling my own swap, but it
just wouldn’t work.

My problems may have had more to do with the suckiness of Oracle than
anything else. Their install script for XE just directs error
messages to /dev/null, so I spent many hours trying to figure out why
the Oracle install “completed successfully” but was broken when I
tried to use it.

You’ve been warned.

Paul


#5

OK thanks everyone! I actually got CentOS 4.4 running flawless on one
of my
servers and everything looked great. Then I followed the OpenVZ install
instructions and it worked fine. I have 3 VPS’s running on this
machine.
And then, suddenly remembering what a linux noob I am, I wondered “What
now?”. :slight_smile:

I could see that I have 3 vps each with their own IPs etc but couldn’t
figure out how I was then going to install my apps on each one etc. I
guess
I really gotta get my head around linux before anything else.

It sounds like I’ll be trying XenExpress to see how it works and
determine
if I’ll need to be buying Xen commercial to go forward (if I use Xen I
need
the multiprocessor and 16gb ram support). When you get right down to it
I
really just want Apache or Nginx running with as many mongrels behind it
as
reasonable. I did set up a successful development server on Windows
with
Apache 2.2 and 5 mongrel services that seems to run fine, but I
understand
that for large scale performance of Rails and MySQL (and the ability ot
automate deployment with Capistrano) that I’d be better off to go linux.
Not to mention that I’ll need about $7000 in Microsoft licenses to go
the
Windows route!!

Thanks again, I’ll keep pushing on and report back as I figure things
out.

Appreciated!

Raul

----- Original Message -----
From: “Paul Stadig” removed_email_address@domain.invalid
To: “Deploying Rails” removed_email_address@domain.invalid
Sent: Friday, February 09, 2007 4:01 AM
Subject: [Rails-deploy] Re: OpenVZ versus Xen or others


#6

Ezra Z. wrote:

I understand there may be a mySQL 4gb per process limit as well. I

without
end-user disruption or the need for costly storage capacity."

http://openvz.org/news/announcements/kernel-2.6.9-stable-20061114

Ummm… Xen can do this too.

“the more you know…” ™

I’ll look into that more.

…pretty cool, huh?

definitely cool, to be able to move a whole VM from one host to
another without any down time is kick ass :wink:

Yeah, I’m also curious if OpenVZ will get accepted into the Linux kernel
as mentioned here:

Since they both approach things slighty different, it’s a good idea to
consider the benefits of both before making a decision.

I really want to go the openvz route with a project we’re working on,
but xen keeps coming back to surprise me.

Robby


Robby R.
http://www.robbyonrails.com/


#7

Ezra! Thanks for the follow up! I was just looking at the
xensource.com
site and found a somewhat buried Xen 3.0 that is open source and doesn’t
have the limitations of the three options on the home page. Is this the
version I should be looking at?

Raul

----- Original Message -----
From: “Ezra Z.” removed_email_address@domain.invalid
To: removed_email_address@domain.invalid
Sent: Friday, February 09, 2007 12:44 PM
Subject: [Rails-deploy] Re: OpenVZ versus Xen or others


#8

Yeah Xen 3.x is what you want.

-Ezra

On Feb 9, 2007, at 12:52 PM, Raul wrote:

I could see that I have 3 vps each with their own IPs etc but
to it I
Not to mention that I’ll need about $7000 in Microsoft licenses to

companies. The OpenVZ server we had with vpslink.com just would not
anything else. Their install script for XE just directs error
On Feb 8, 11:52 pm, Robby R. removed_email_address@domain.invalid

running on a test server right now. I’ll be testing two
two
could buy commercial Xen but I found OpenVZ (open source
server has it’s own kernel running with Xen… which will take
product is
end-user disruption or the need for costly storage capacity."

*http://linux.slashdot.org/article.pl?sid=06/01/17/2251233
Robby

– Ezra Z.
– Lead Rails Evangelist
– removed_email_address@domain.invalid
– Engine Y., Serious Rails Hosting
– (866) 518-YARD (9273)


#9

Raul-

I’m not sure what makes you think you need the commercial Xen for
anything you mention. We run the open source Xen on boxes with 16Gig+
Ram and 4 processor cores. There is no limitation to the open source
Xen afaik it can easily address 64Gigs of ram and many processors.

-Ezra

On Feb 9, 2007, at 9:26 AM, Raul wrote:

to it I
Not to mention that I’ll need about $7000 in Microsoft licenses to

companies. The OpenVZ server we had with vpslink.com just would not
the Oracle install “completed successfully” but was broken when I

cluster,
virtualization a bit to see what the benefits might be and it
guidance would be appreciated.
works
administrators to move virtual servers between physical servers

Robby


Robby R.http://www.robbyonrails.com/http://www.planetargon.com/

– Ezra Z.
– Lead Rails Evangelist
– removed_email_address@domain.invalid
– Engine Y., Serious Rails Hosting
– (866) 518-YARD (9273)


#10

I too have been playing around with the different virtualization
possiblities, and I believe it all comes down to one choice. OpenVZ
is easier to get going but doesn’t guarantee that the hoster is not
overselling. Xen is harder to get going (in my experience, due to pae
quirks and other stumbling blocks) but once you get it going it’s just
as easy to use and gives the customer the added satisfaction that
he’ll be using dedicated hardware resources that the host machine
actually has, rather than overlapping limits like you can with OpenVZ.

I will be launching a vps hosting service in the next month or so but
I have a lot more testing to do before I’m satisfied with my final
choice. The hosting service will be aimed at rails development, not
production. More details to be announced very soon.


#11

Thanks for the guidance Ezra!

Raul

----- Original Message -----
From: “Ezra Z.” removed_email_address@domain.invalid
To: removed_email_address@domain.invalid
Sent: Friday, February 09, 2007 12:59 PM
Subject: [Rails-deploy] Re: OpenVZ versus Xen or others


#12

Did anyone read the HP Labs report? Any performance issues with Xen?


#13

Hello Fernando.

We use Xen at Engine Y., and have thousands of instances.

We don’t experience any abnormal performance issues that we associate
with Xen.


– Tom M., CTO
– Engine Y.

On May 27, 11:07 am, Fernando P. <ruby-forum-incom…@andreas-