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Virtual storage appliances: A good fit for SMBs

Solution provider takeaway: Virtual storage appliances enable resellers to deliver advanced server virtualization functions to SMB customers that can't afford networked storage. 

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Once you get past the basics of server consolidation, what makes virtualization technologies sizzle? With VMware, it's VMotion for live server migrations, Distributed Resource Scheduler (DRS) for automated load balancing, VMware Consolidated Backups (VCBs) for centralized backup and Site Recovery Manager (SRM) for disaster recovery planning. For the most part, all of these solutions require one key building block: networked storage.

This requirement is a key obstacle for many small and medium-sized businesses (SMBs). In fact, Enterprise Strategy Group (ESG) reports that 47% of virtualized servers in SMB data centers (companies with fewer than 1,000 employees) are not attached to networked storage.

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Your SMB customers more than likely want the advanced features of server virtualization but can't afford or justify the expense of networked storage. This gap creates a perfect scenario for you to introduce a virtual storage appliance. Such a product can provide a platform that houses the servers that your customer needs to host virtual machines, and those same servers can be the shared storage.

Companies like LeftHand Networks and FalconStor are entering virtual storage appliance territory, and more will follow. The appliances are essentially a version of the companies' storage solution that runs as a virtual machine; this virtual machine is then activated on each physical host, and the hosts are connected via an iSCSI connection.

Implementation of virtual storage appliances will differ by vendor. For instance, FalconStor's configuration calls for a primary storage server that the other hosts connect to via iSCSI. The primary host should be provided with extra CPU resources and memory to handle the additional load placed on it. The FalconStor product can be mirrored to a second server for high availability.

LeftHand's virtual storage appliance, on the other hand, spreads the I/O load across each physical host in the cluster. As a result, each node will need more compute and memory resources than the secondary hosts in the FalconStor setup, but you won't need to mirror to a second server locally since the data remains 100% available if one node fails.

With virtual storage appliances, your customer gets all the capabilities that they would get from each company's hardware-based storage system. Features like shared logical unit number (LUN) access (which is required for Vmotion), snapshots for data protection, replication (required for SRM) and thin provisioning are all available with a virtual storage appliance.

Shared storage with VMware also enables customers to take advantage of the enhanced data protection capabilities of VCB. The tool allows the backup application to launch a backup of a specific virtual machine by communicating with VMware's VirtualCenter management console and the appropriate ESX server to prepare the virtual machine for backup. The virtual machine flushes pending I/O operations, and a redo log is created for each virtual disk to be protected. Once created, the virtual machines can be returned to their normal state. The backup proxy then mounts the virtual machine disk files and allows the backup agent to send a copy across the network to the backup server, which then writes the stream to the backup target.

VCB provides significant benefits: no resource load on the virtual machines, the ESX host server itself or the messaging network; decreased concern over the backup window because there is little impact on running applications; and file-level restores while exporting the encapsulated virtual machine. As a result, backups (including simultaneous file-level and DR backups) can occur during the middle of the workday with no impact on the ESX environment or the primary network.

With shared storage and the physical hosts in place, your customer merely needs to load the virtual machines onto the physical hosts. Because the physical hosts are connected via an iSCSI connection, the shared storage is automatic and with it comes the full capabilities of VMware.

The opportunity for you is that a virtual storage appliance means a customer will have three different components provided by three different vendors: VMware, the storage appliance software manufacturer and the physical server hardware. Someone needs to integrate these components into a turnkey solution. SMBs likely don't have the resources, time or expertise for the task and so they desperately need the help of an integrator.

As mentioned earlier, when configuring these solutions, extra attention should be placed on the memory and processing capabilities of the server hardware. Obviously, this is a key concern in any server virtualization effort but even more so in the case of virtual storage appliances. Make sure to budget extra headroom to handle the higher I/O requirements of these appliances.

Additionally, since one or more -- depending on the storage appliance solution -- hosts will also house the storage for the virtual infrastructure, extra attention should be paid to this storage as well. While SATA will work, it most likely should be Fibre Channel or SAS for increased performance and reliability. It will also need to be of significant capacity; factor in 30% to 50% additional storage capacity to handle snapshots and mirroring. In some cases you will want to count on internal RAID or mirroring for disk redundancy, so factor in the correct controller for your physical host servers.

Finally, don't forget the fact that these additional capabilities enabled by the shared storage will also require additional headroom. Once you've given your customer the ability to use a function like VMotion, they are going to use it. Make sure that the server they migrate to will have the headroom to handle the additional workload.

Virtual storage appliances give resellers the ability to turn a customer's bare-bones VMware implementation into a full-featured VMware infrastructure, by delivering shared storage in a relatively painless way. This solution not only does great service to customers but also broadens the application of server virtualization, making it approachable for a larger audience of businesses.

About the author
George Crump is president and founder of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. With 25 years of experience designing storage solutions for data centers across the United States, he has seen the birth of such technologies as RAID, NAS and SAN. Prior to founding Storage Switzerland, George was chief technology officer at one of the nation's largest storage integrators, where he was in charge of technology testing, integration and product selection. Find Storage Switzerland's disclosure policy here.


 

This was first published in October 2008

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