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Why DVT Matters in the Overland Storage REO

Have you ever looked at a technology solution that left you wondering why a specific technology matters?  I often look at a technology solution and take note of its many features but then may walk away thinking it was a slick presentation but wonder why I should care about it? So when I evaluate a technology solution, I first look to see if it solves a real problem. This can include making me more productive, addressing a key operational pain point or in some way reducing operational costs.

Such were my thoughts when I considered Overland Storage’s Dynamic Virtual Tape (DVT) feature on the REO series virtual tape libraries (VTLs). It offers several advantages over the standard method of creating virtual tape cartridges that are only of a fixed size including:

·         Ease of management

·         Efficient use of storage capacity

·         Less overhead associated with replication


DVT is thin provisioning for Virtual Tape Libraries and brings the same advantages that thin provisioning brings to SAN-attached storage as it reserves exactly the amount of storage capacity that you need for your backup jobs.  This removes the guesswork from provisioning space on VTLs that one normally encounters using VTLs without DVT. (How large should I make each virtual tape cartridge? How many virtual tape cartridges should I make of that size? Etc.)

Using DVT, each virtual tape cartridge only reserves a 1 GB of initial capacity and then dynamically scales as high as you set your upper threshold. (If you do not set an upper limit, the dynamic virtual tape cartridge has a maximum capacity of 2 TB.) This makes it easier for administrators to introduce a REO VTL into their company’s infrastructure without spending an inordinate amount of time configuring and managing the VTL and it saves money since DVT conserves disk space on the REO VTL.

Another advantage DVT has over traditional approaches to VTLs is replicating virtual tape cartridges to a secondary off-site VTL. Using a static virtual tape cartridge, the underlying storage system is ignorant of the blocks of data in use on the virtual tape cartridge. So if you have a 40 GB virtual tape cartridge that you wish to replicate, the VTL may replicate all 40 GB of the virtual tape cartridge since VTLs tend to replicate data at the block level. So whether the virtual tape cartridge is full or only has one byte of data on it, all blocks on the virtual tape cartridge are replicated regardless of how much data is actually stored on the virtual tape cartridge. 

Using DVT, the REO is aware of how much data is stored on the virtual tape cartridge. This also comes into play in replicating the blocks of data to a REO at another site. Rather than replicating all of the blocks of data on the cartridge, it only replicates the amount of data that is actually stored on each virtual tape cartridge. This reduces the overhead on the VTLs that they need to send and receive the blocks, the amount of storage capacity needed on each VTL and the amount of network bandwidth needed to transmit the blocks of data. 

The cost savings seen by the introduction of thin provisioning in storage systems are well documented and it stands to reason that companies will realizes these same savings by using the DVT found in Overland Storage’s REO VTLs. DVT eases the REO’s initial configuration, simplifies its ongoing management, more efficiently uses storage capacity and contributes to reducing the amount of data that companies need to replicate when sending data offsite.

REO’s DVT value proposition is also felt up front since it makes it easier for you to introduce disk-based backup into your environment by initially making your backup jobs more manageable. All told, DVT should result in tangible efficiencies and cost savings that should make both you, and your boss, pleased with the benefits of introducing REO’s DVT into your backup environment.


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