Several years ago, storage virtualization technology would be a hard sell for the small and midsized (SMB) space, but that is no longer true today. In fact, I've seen storage virtualization as a very logical complement
Data and storage management is one tough aspect of server virtualization deployments. Many organizations find meeting backup window requirements following a server virtualization-based consolidation project to be difficult. The difficulty usually stems from CPU, storage and network I/O contention, since servers that previously sent backup data over dedicated hardware now have to use shared physical devices for backup I/O. Storage resellers can alleviate backup and data protection problems that are frequent with new server virtualization deployments by bundling storage virtualization and server virtualization as a single complementary solution, to be discussed further in an upcoming tip.
Many organizations respond to backup challenges by incorporating serverless backups into their data protection strategy. This can be done using a "backup proxy" server over an iSCSI or Fibre Channel storage area network (SAN), or by using snapshots along with block-level replication. Ultimately, the end result of a serverless backup is that backup processing and I/O can be offloaded from a virtual machine's (VM) physical host server to another server with access to the VM's storage. Offloading backup processing and coordinating data protection jobs without impacting virtual machine host servers is much easier when a storage virtualization technology is deployed to complement the existing server virtualization infrastructure.
In-band storage virtualization appliances, especially software-based solutions from vendors such as DataCore and FalconStor, are very good fits for the SMB market. Many server virtualization deployments involve the decommissioning of older servers in favor of new hardware. Oftentimes, decommissioned servers are Pentium 4-class systems that are only a couple of years old. P4 processing and a couple of gigabytes of RAM can make for a very powerful storage virtualization appliance at little cost. Since the appliance would run on repurposed hardware, the only upfront cost of deploying storage virtualization would be the cost of the storage virtualization technology software. Products such as DataCore's SanMelody start at less than $1,000, making storage virtualization even a good fit for the cost-conscious business.
Why virtualize storage?
Storage virtualization technology offers more than just having something to do with decommissioned hardware. With a storage virtualization appliance, organizations can pool and consolidate storage resources, while adding a layer of transparency between storage and connected servers. Virtualization appliances cache frequent data requests, which oftentimes provides improved I/O performance. Many often jump to the assumption that inserting anything the in the data path leads to added latency.
To me, the greatest benefit of deploying storage virtualization appliances is the added data protection. Storage virtualization appliances offer the following data protection options:
- Transparent data migration
- Synchronous disk mirroring and automatic failover
- Point-in-time snapshots
- Asynchronous IP mirroring
Since storage virtualization appliances add transparency between physical servers and physical storage, data volumes can be moved to new storage locations without impacting the production physical servers.
Synchronous mirroring can be used to maintain two redundant data sets. This way if a server's primary volumes fail, the server would be redirected to the secondary mirrored volumes.
With point-in-time snapshots, data can be quickly secured throughout the day. Advanced agents installed in a VM's guest operating system can quiesce applications prior to the start of a snapshot in order to ensure data consistency. Typically, advanced agents are used when a VM is configured with raw storage, which connects VMs directly to storage LUNs. If a VM uses virtual hard disks, administrators can use a script to suspend a VM, create a snapshot, and then resume the VM. Of course, if the VM cannot be shut down, then VM's data can be backed up using traditional backup agents.
Asynchronous IP mirroring can be used to synchronous production VM data with standby VMs at a remote site over a wide-area network (WAN). In doing so, DR protection and subsequent recovery could be automated.
It's hard to ignore the benefits of storage virtualization. The hardware transparency provided by server virtualization has been long embraced by IT professionals, but many are ignoring the same benefits which are provided by storage virtualization. If you've been scared off by storage virtualization sticker shock in the past, the low-priced enterprise-class software storage virtualization products on the market today are worth another look.
About the author: Chris Wolf, MCSE, MCSE, MCT, CCNA, is a Microsoft MVP for Windows Server-File System/Storage and the Computer and Information Systems Department Head for the ECPI College of Technology online campus. He also works as an independent consultant, specializing in the areas of virtualization, enterprise storage, and network infrastructure management. Chris is the author of Virtualization: From the Desktop to the Enterprise (Apress), Troubleshooting Microsoft Technologies (Addison Wesley) and a contributor to the Windows Server 2003 Deployment Kit (Microsoft Press).
This was first published in June 2007