Bare metal virtualisation and host-based storage (metal/host)
Personally, I think this scenario is the hardest to manage. In
this case, you're running VMware ESX server on the bare metal and storing the
individual virtual machines on local disks. You have the same risks and
recovery limitations inherent in the host/host model, but you do not get the
benefit of backing up the individual virtual machine files without using third-party
software.
Your best option for this scenario is to individually back up each virtual machine as if it were a physical server. That is, use NTbackup, or install your backup software's agent.
Bare metal virtualisation and shared storage (metal/shared)
This is, by far, the most desirable -- and the most expensive -- way
to implement a robust virtualised environment in your organisation. In this
scenario, you get all of the great benefits of the host/shared method (snapshot
capability, etc), but, with VMware ESX, you also get incredible features
including VMotion, VMware HA (High Availability), and VMware DRS (Distributed
Resource Scheduler).
VMotion allows you to seamlessly move a running virtual machine between ESX hosts. HA watches your ESX hosts and, upon detection of a host failure, automatically moves guests from the failed host to other servers in the cluster. DRS automatically moves virtual machines between suitable ESX hosts based on the resource requirements of the virtual machine. DRS also provides a "maintenance mode" option whereby, with minimal effort, you can force DRS to move all guests from a host node so you can perform maintenance on that node.
All of the features require shared storage in the form of a supported Fibre Channel or iSCSI SAN or NAS device.
Summary
A robust, scalable, highly available virtualised environment
can save an organisation significant time and money, but you need to carefully
plan your virtualisation storage strategy and decide which approach is best for
your company.
|
|
Host-based virtualisation |
Bare metal virtualisation |
|
Host-based storage |
Host/Host |
Metal/Host |
|
|
Pro: Cheap (the virtualisation software is free). |
Pro: The local storage is cheap. |
|
|
Pro: The local storage is cheap. |
Con: The virtualisation software is expensive. |
|
|
Pro: Easy to deploy. |
Con: Without 3rd party tools, limited to traditional backup methods.
|
|
|
Con: "Eggs in one basket" -- lots of VMs on a single host. |
Con: "Eggs in one basket" -- lots of VMs on a single host. |
|
|
Neutral: Can back up whole VM with regular file backup tools or use an agent in each VM. |
|
|
|
Con: Underlying OS overhead. |
Pro: Little underlying OS overhead. |
|
|
Best bet for "proof of concept" virtualisation projects. |
Best bet for small virtualisation projects. |
|
|
|
|
|
Shared storage |
Host/Shared |
Metal/Shared |
|
|
Pro: Virtualisation software is free.
|
Pro: Extremely robust. |
|
|
Con: Storage is fairly to very expensive. |
Con: Most expensive option: Storage is fairly to very expensive. The virtualisation software is expensive. |
|
|
Pro: Recovery is a manual process but can be done fairly easily when configured right. |
Pro: Highly available. Load balancing (DRS). |
|
|
Con: Underlying OS overhead.
|
Pro: Little underlying OS overhead. |
|
|
Best bet for virtualisation projects for which software costs must be kept to a minimum and enterprise-grade recovery is not necessary. |
Best bet for enterprise-grade virtualisation projects where availability is key. |
TechRepublic is the online community and information resource for all IT professionals, from support staff to executives. We offer in-depth technical articles written for IT professionals by IT professionals. In addition to articles on everything from Windows to e-mail to firewalls, we offer IT industry analysis, downloads, management tips, discussion forums, and e-newsletters.
©2006 TechRepublic, Inc.
