[geeks] Virtualization Smackdown

[Patrick Giagnocavo]

I have used VMware, Xen / XCP (now XenServer 6.2 after it got open sourced), OpenVZ, and KVM.

First, the highest performance you will get, is from OpenVZ - provided you can live with its limitations.  

Reason:  while each VM gets its own view of the filesystem, it is really just 1 filesystem to the host node, and OpenVZ will use any excess RAM as disk cache or other buffer cache.  

Plus you are running just 1 kernel image, with each VM having security context or whatever the Linux kernel calls it, to wall-off each VM from the others.

Backups are easy to do, and, if you have root login on the host-node you can easily get into any VM, even manipulate files from the host-node for each VM, etc.

XenServer (free or paid support) would be my second choice, with the caveat that some pieces are fiddly. Things I don't like about XenServer are the "let's use UUIDs for everything" and the rather opaque way that local storage for each VM is handled;  if you have a boot problem or other issue, it can take some Google-fu to find out what has gone wrong and how to then fix it.

Another issue with XenServer is that PV hosts will perform much better - which means, you have to run the versions of Linux that are supported by the guest-tools packages they ship.

Once you get everything working properly, though - it has shown itself to be very stable.

Nice thing:  auto-snapshots that you can also set up to auto-archive to an NFS or Samba store.

VMware, is the most rock-solid of all IMHO.  Local storage is its weak point - I wasn't happy running VMs on it without a 1GB caching RAID controller and fast SAS disks. It might be, with SSDs being so low in price now, that an easy fix is just to run SSDs.  Alternatively, NFS storage of VMs worked but was slow-ish; iSCSI was fast but, any blip in networking can cause issues from what I understand.  I think in the last experience I had, I ran ZFS on Solaris and turned off the NFS write-sync feature for performance reasons (VMware forces a sync on every NFS write, or at least used to).

KVM works, but I haven't been very happy with it in terms of monitoring what is going on and trying to figure out performance issues. It is really bad with older Linux kernels, so if you have anything "legacy" sitting around, use VMware.

Hope this helps,

Patrick

----- Original Message -----
From: "Mark Benson" <md.benson at gmail.com>
To: "The Geeks List" <geeks at sunhelp.org>
Sent: Wednesday, October 15, 2014 12:36:16 AM GMT -07:00 US/Canada Mountain
Subject: [geeks] Virtualization Smackdown

Hi,

We're planning a large systems move at work to something running on
Python/Postgres and it means our new production server (8-core Xeon Dell
Poweredge T610) is going to have to support 2 environments, the new one and
a LAMP environment.

While we have as second server (HP ProLiant ML310e v2 Gen8) I'd like to use
that as some form of redundant fallback to add failover capacity.

I also have a HP Microserver that I use for Dev that would ideally need to
support both so I can putz about with them in isolation.

Somewhere in the production environment I'd like also like an isolated LAMP
server to host an internal version of our website so we have a reference
version, and also a Samba server for sharing files between desks.

We don't plan on using Windows on the server side at all.

I'd like to virtualise them to keep instances of MySQL and Postgres from
fighting each other for resources. I've looked into the whole thing and
narrowed it down to using:

Xen
Kvm
VMWare vSphere Essentials

I have very little VM experience aside from Virtualbox and some tinkering
with Xen.

Xen's great if you use XenServer but it's a bitch to patch unless you buy
support (too expensive), or it's easy to patch but a cow to manage if you
use CLI tools.

Never used KVM.

VMware has a solid reputation, isn't that expensive and Essentials covers 3
machines and 6 sockets, which is a perfect fit. I've never used it either.
The only downer is it's on a rolling support contract

I'd appreciate advice from anyone who's used any or all those environments
as to relative advantages and drawbacks. We're a small company and don't
have pots of money.

--
Mark Benson

http://markbenson.org/blog
http://twitter.com/mdbenson
http://twitter.com/dectecinfo
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