When it comes to setting up storage virtualization and virtualizing servers in general for the SMB market, the jump to a virtualized infrastructure is not as easy it has been for larger infrastructures. In this article, Ill explain the storage virtualization challenges of the SMB, providing guidance on how to go the extra distance to reach virtualization nirvana.
What are the first thoughts that come to mind when it comes to server virtualization? For most, it is simply the decision between Hyper-V, Xen or vSphere.
When it comes to actually taking the server infrastructure of the typical SMB and going virtual across the board, a slew of issues arise that are at times more difficult to address on the smaller scale.
First, It really doesnt matter which hypervisor to implement. For many SMB installations, especially less than five servers, any of the products will perform to an acceptable level at the end of the day.
The number one issue that needs to be addressed when it comes to virtualization for the SMB is storage. Consider that the typical SMB may be forced to start with virtualization only via free offerings such as ESXi without vCenter, Hyper-V without System Center Virtual Machine Manager (SCVMM) or XenServer.
Regardless of the virtualization engine in use, the storage decisions are very important for the SMB. The migration to storage virtualization is further complicated for the SMB as there may not be an existing shared storage infrastructure. Shared storage is the one of the most critical design elements of virtualization environments, big or small. Storage is one of the core four resource categories alongside processor, network and memory.
For the SMB, what options are available for shared storage that can be used to virtualize servers? In short, there are plenty storage choices available.
Many organizations may first be tempted to use direct attached storage (DAS) for virtualization. DAS is fine for a proof of concept for virtualizing servers, but we have to step back and evaluate the objective of server virtualization and how using DAS impacts this task.
One of the core goals of virtualization is to abstract operating systems (or servers) from hardware. If a vSphere, Hyper-V or XenServer host is providing virtual machines on a single DAS array, we have only partially abstracted the operating system from the hardware. Shared storage via some form of storage area network (SAN) or network attached storage (NAS) device can entirely abstract the operating system from the underlying hardware.
If DAS is used, there is a well-defined single point of failure if the server fails. To be fair, DAS arrays are usually very powerful in terms of I/O controller and number of drives. Even for the smallest virtualized infrastructure, if we can introduce the concept of a cluster of hosts with shared storage, we have truly abstracted the operating system from the server.
So, how do we select the right storage product for virtualization in the SMB? There are a number of factors to take into consideration, here are key decision points:
Connectivity: Fibre channel is fast, but iSCSI and NFS are much less expensive per port.
Number of drives: The more drives serving data in an array, the better the throughput.
Drive type: SATA drives offer a lot of space at an attractive price, but SAS drives outperform.
Not to shop by usable space: Simply selecting a product to meet the size requirements will not address performance and scalability for virtualization.
Hypervisor compatibility: Each product has a wide array of supported devices to run virtual machines. Hyper-V via Windows Server 2008 will have the broadest support, followed by vSphere and XenServer.
It is important to note that if Hyper-V with SCVMM and clustered shared volumes will be used, the storage product will need to support SCSI-3 persistent reservations. Many products do not have this level of support yet are labeled as supported for Hyper-V. Ask the questions ahead of time!
When it comes to selecting the right product, be prepared to spend some money. While a single disk drive may be quite inexpensive, costs go up when all of the components are rolled into a comprehensive solution.
These costs include a storage processor (controller), SAN switches if needed, additional Ethernet ports if needed, and licensing and support costs, which vary by product. As a fair warning, be advised that you can always buy lesser expensive storage. There are performance trade-offs to purchasing lesser-expensive storage, however.
There are plenty of products in the space from familiar names on the server side such as Dell and Hewlett Packard. The two server stronghold companies have storage offerings that can easily allow the SMB to roll shared storage into the product portfolio.
The SMB would be wise to also consider products from Overland, Drobo, Iomega and NetApp. Beyond traditional storage controller devices, software-based storage products such as FalconStor, Datacore, Openfiler, Nexenta and StarWind can take any traditional server and turn it into a SAN storage controller.
All of the major storage suppliers can provide disk. But depending on the needs of the virtualization installation, any of the available features may be a deciding factor for what solution to use.
One popular feature is data deduplication. Deduplication, if applied on the block-level of the storage system, will search for like blocks on disk and treat those as a single instance of the storage. Virtualization is made for deduplication by use of virtual machine templates and like operating systems. Chances are, each virtual machine is not very different from the next from the system level.
For Windows virtual machines, this is primarily the C: drive; making a great deduplication opportunity. NetApp storage, for example includes data deduplication with each of the FAS series storage products and offers the deduplication guarantee program to ensure you get 50% or more deduplication benefit.
Other features of interest include protection offerings such as volume replication and snapshots. These storage options are available on higher-featured products, but also for smaller storage products for the virtualization installation for the SMB.
One new product is the HP StorageWorks P2000 G3 Modular Storage Array (MSA). The P2000 MSA controller has evolved from the G2 and previous editions to offer two critical new features that can fit the SMB virtualization implementation well. The first new feature is a dual-personality connectivity option. This allows the P2000 MSA to connect simultaneously to fibre channel and iSCSI networks. Administrators can then provision the systems that need the higher throughput to use fibre channel and less critical systems to connect via iSCSI.
The P2000 MSA also includes volume snapshots. Like a virtual machine snapshot, a volume snapshot takes the whole logical disk and tracks the changes forward from a point in time. There are 64 snapshots included with the product, additional licensing can raise the limit to 512 snapshots.
Thin provisioning of the storage is also a feature that is available on most storage products, and is almost a requirement in todays provisioning practices. If the storage system does not provide thin provisioning of volumes, each of the major hypervisors can thin provision the virtual machine disk files.
There is no silver bullet to easily and clearly determine which storage product is right for the SMB to use for virtualization. There are a number of reviews available for products that can be used, but the best single piece of advice is to identify the storage features you need and select the storage product based on those requirements.
Shopping by price and usable storage amounts will get you in trouble quickly.
Rick Vanover, VCP, MCITP, MCTS, MCSA, is an IT Infrastructure Manager for Alliance Data in Columbus, Ohio. He is an IT veteran specializing in virtualization, server hardware, operating system support and technology management. Follow Rick on Twitter at @RickVanover