Friday, March 7, 2008

EMC announces mainframe Virtual Tape Library (VTL) product

Last Month EMC announced their entry into the mainframe Virtual Tape Library market:

EMC Corporation (NYSE:EMC), the world leader in information infrastructure solutions, today extended its industry-leading virtual tape library (VTL) capabilities to customers in mainframe environments with the introduction of the EMC® Disk Library for Mainframe (EMC DLm). Delivering the industry's first 'tapeless' virtual tape system for use in IBM zSeries environments, the EMC DLm enables high-performance disk-based backup and recovery, batch processing and storage and eliminates the challenges associated with traditional tape-based operations to lower customers' data center operating costs.”

“The EMC DLm connects directly to IBM zSeries mainframes using FICON or ESCON channels, and appears to the mainframe operating system as standard IBM tape drives. All tape commands are supported by DLm transparently, enabling customers to utilize their existing work processes and applications without making any modifications. Additionally, the EMC DLm enables asynchronous replication of data over IP networks, extending the benefits of array-based replication to mainframe data protection operations.” [Source: EMC press release]

This is an interesting strategic move by EMC. Not only does it offer EMC entry into a portion of the mainframe storage market where they couldn’t play before, but in the longer term it may also tend to further solidify vendor allegiance in the mainframe storage market as recovery methodologies tend to be somewhat vendor centric.

A “tapeless” implementation of virtual tape is an interesting proposition, but it is not without its own unique constraints. Seeing how Murphy was, and always will be an optimist, it will be interesting to see how “tapeless tape” plays out in the real world.

First of all, a VTL implementation consisting of a disk buffer and no “back-end” physical tape tends to ignore the most attractive cost point of storing data on tape. Namely, that of data being stored – unused – for deep archive or other purposes. Data of this type that eventually resides on physical tape can be stored on the shelf for mere pennies/GB/month. However, if there is no “back-end” physical tape that can be ejected from the VTL, then the unused data must be up and spinning – perhaps forever – at a higher cost per GB/month.

A second consideration is one of capacity. Tape usage in a mainframe environment tends to be somewhat inconsistent. There are the normal cycles of “weekly backups” and “month-end jobs” and the like, but there are also the unplanned events that can use hundreds or thousands of “tapes” without warning.

Is there a mainframe shop that hasn’t run out of tapes in recent history? Even for those mainframe environments that are running VTLs today and never plan to eject the physical tape media... They can eject it should the need arise to add additional capacity on an emergency basis.

These two points are certainly not the most issues to be addressed when evaluating tape solutions. They are merely a couple of additional items to be considered along with cost, performance, availability and other components of the total solution.

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