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Overland Storage Brings Thin Provisioning to VTLs

Configuring, allocating and then managing storage capacity on storage systems has been to date been a very tenuous proposition. Companies either allocate just enough storage capacity to get by but then spend lots of time managing it or they overprovision storage in order to satisfy initial storage requests but then waste much of the allocated storage capacity. As anyone close to storage knows, either approach amounts to very costly and inefficient ways to manage their storage capacity.

To address this, thin provisioning has recently emerged as a way for storage systems to only reserve the storage capacity that is actually needed. By monitoring when data is written to a storage system, it eliminates the need to allocate extra, unneeded storage capacity for an application. In so doing, thin provisioning provides a more efficient and cost effective approach to storage capacity management. However to date thin provisioning has been the exclusive domain of a few NAS and SAN based storage systems.

Overland Storage changes this. It represents one of the first, if not the first, virtual tape library (VTL) provider to include thin provisioning as part of its REO series VTL offering. Known as Dynamic Virtual Tape (DVT), virtual tape cartridges can now dynamically increase or decrease in capacity as backups demand. Formatted this way, virtual tape cartridges only use as much of the REO’s real storage capacity as it needs.

Overland Storage’s DVT provides administrators with two configuration options:

  • Static
  • Dynamic

Static is the traditional way that VTLs are configured which the REO VTL does support. In a static configuration, each virtual tape cartridge is assigned a specific storage capacity (20 GB, 40 GB, etc.). The REO includes this static option since there may be a requirement by some applications for a fixed virtual tape cartridge size. However the static setting is not an “all-or-nothing” setting across the REO VTL so companies only need to configure some of the virtual tape cartridges in this fashion, if they use it at all.

It is the dynamic setting that should interest more companies anyway. All virtual tape cartridges configured as “dynamic” reserve an initial capacity of 1 GB. Then, as data is written to this virtual tape cartridge by the backup software during backup periods, the virtual tape cartridge dynamically grows in size to house all of the data in the backup job. Equally interesting, as the backup jobs expire or data is copied from the virtual tape cartridge to a physical tape cartridge and the data deleted, the virtual tape cartridge automatically shrinks in size back to its original 1 GB size.

The REO does include some measures to prevent virtual tape cartridges configured as dynamic from growing to exorbitant capacities. Companies can optionally set an upper threshold (20 GB, 80 GB, 200 GB, etc) so that once the virtual tape cartridge reaches that capacity, backup data is then placed on another virtual tape cartridge. If no maximum capacity for a virtual tape cartridge is defined, the virtual tape cartridge defaults to the maximum size of 2 TB.

Using REO’s DVT, companies no longer need to rely on over provisioning, manual intervention or even new technologies like deduplication as their primary means to keep storage capacities on their VTLs under control. Overland Storage’s application of the principles of thin provisioning to virtual tape on its REO VTL gives companies a new option for control over their storage infrastructure while maintaining the backup and recovery speeds that backup to disk is expected to provide.


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