Server virtualization can bring tremendous benefits to an environment if implemented properly. As a value-added reseller, you have a good opportunity to help a customer get on track with a virtualization pilot. Your sound advice and planning can then help a customer move from a pilot implementation to a full-blown, flexible, virtual environment.
Keep in mind one of the advantages of virtual machines is their portability; once a customer has decided that everything is running smoothly with the pilot, they can migrate virtual machines to a production environment in a relatively short amount of time.
No matter which virtualization vendor's product you plan to implement, you will want to decide a few things right from the start so you can make a smooth transition from the pilot to wide-scale production: virtualization targets, storage strategy and server capacity.
Server virtualization targets
First help your customers decide which servers they would ultimately like to virtualize. Ancillary servers like DNS, domain controllers (in a small to medium Active Directory environment), DHCP, and file and print servers tend to be the low-hanging fruit. These types of servers generally do not take full advantage of the hardware on which they run and are perfect targets for virtualization. Beyond that, Intranet Web servers and small database servers can make good targets.
It is important that you provide benchmarking services to customers as part of the virtualization pilot assessment. By measuring processor utilization, memory utilization and disk I/O on potential virtualization targets, you help the customer make an intelligent decision on which servers to virtualize. While more complex servers, such as application servers or database servers should be included or excluded in the list of virtualization targets from the beginning, the pilot should probably virtualize the low-hanging fruit, such as the ancillary servers and
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low-utilization file servers mentioned above.
Storage strategy for virtualization pilot
Choosing a storage strategy before implementing a virtualization pilot will allow your customer to make decisions on how to progress after the pilot. As a VAR, you should let the customer know the pros and cons of direct-attached storage (DAS), network-attached storage (NAS) and storage area networks (SAN), both iSCSI and Fibre Channel. The type of storage selected might determine what virtualization technology to use.
For traditional server virtualization, VMware is still the leader; customers have a couple of choices with this company. If only ancillary servers are virtualized in the pilot and beyond, VMware's Virtual Server product might be a good fit. The customer will not be able to use Vmotion or any high availability features that come with it. However, for ancillary servers, some downtime for a manual switchover to another physical host machine may be acceptable. In this case, DAS or NAS might be perfectly suitable. For example, if the customer virtualizes Active Directory domain controllers on two separate host machines, the highly available infrastructure is already there. The same goes for DNS server pairs. Also, DHCP servers being unavailable for a few minutes while you switch the virtual machine over to another physical host is usually not a big deal unless all of the DHCP clients happen to be renewing their IP addresses at the time of failure.
If the customer plans to virtualize more critical servers that do not have natural failover partners (domain controllers have natural failover partners and are included in ancillary servers for this reason), VMware's Virtual Infrastructure 3, including ESX Server, Virtual Center, Vmotion and High Availability feature might be the best option. This is a more expensive offering, but it gives the customer piece of mind knowing that the virtual machines will automatically fail over to another ESX Server if hardware failure should occur.
For this to work, some sort of shared storage device (usually a SAN) is required. Although, it should be noted that Chuck Nollis, vice president of Technology Alliances at EMC, recently posted this to his blog: "I think that, in the long term, we'll find high-end NAS much more friendly for high-end VMotion/DRS farms than today's SANs." We will see if this is true as NAS technology and server virtualization technology advances. If the customer would like to start small with VMware Virtual Server and later move to ESX Server, they could use the VMWare Converter tool to migrate the Virtual Server virtual machines from VMware Virtual Server to ESX Server.
If the customer plans to virtualize high-end database or application servers, or servers on the same operating system, they might want to look at OS virtualization with a product like Virtuozzo. In this case, DAS or a SAN could be used feasibly. From the Virtuozzo Web site: "Virtuozzo migration capabilities allow VEs to be moved in real-time with near-0 downtime (keeping the application available through the migration until the last few seconds), and no SAN is required." This could prove to be a real value for customers who do not have a heterogenous environment or need near-native virtual instance performance with high availability.
Server capacity for virtualization pilot
Your customer's storage strategy may determine some aspects of the server capacity strategy. For instance, if DAS is used servers will have to be specified accordingly with either internal storage, or external SCSI or SAS adapters. If iSCSI or Fibre Channel is used, the customer might want to invest in an iSCSI HBA (for added iSCSI performance and less processor overhead on the host machine). They must invest in Fibre Channel HBAs if Fibre Channel is used. With iSCSI, a software initiator might be used in lieu of an HBA if not much performance is needed.
The virtualization targets will also determine server capacity. For example, the customer will not want redundant domain controllers used for Active Directory on the same physical host machine, so if the host machine fails, the other domain controller will still be active. As a VAR, you can help the customer during the capacity planning process by suggesting appropriate, balanced workloads for the physical hosts that the virtual machines will be running on.
About the author: Harley Stagner has a wide range of knowledge in many areas of the IT field, including network design and administration, scripting and troubleshooting. Of particular interest to Harley is virtualization technology. He was the technical editor for Chris Wolf and Erick M. Halter's book Virtualization: From Desktop to the Enterprise and currently writes his own blog at www.harleystagner.com. Harley is also SearchSystemsChannel.com's featured virtualization expert. Ask Harley a question today.
