On the other hand, if you have a tape library mainly to keep a local copy readily accessible in a near-line mode, then the decision to split into two separate local tape libraries versus one large one comes down to performance, availability, capacity and economics. While most tape libraries today from vendors such as Hewlett Packard (HP) Co., IBM Corp., Quantum Corp. and Sun Microsystems Inc. support well in excess of 3 PB each, your other consideration is how many tape drives can be supported along with the supported tape slot capacity per modular footprint (e.g., cabinet).
Also consider what types of tape drives are supported such as LTO, DLT, AIT, DDS and Travan, and if there is a single or multiple robotics handling mechanism that could be a bottleneck for your specific use. While a single library could be the solution, look into its capabilities to verify that it does not or will not produce any performance or availability contention issues for your environment. Keep in mind that when shipping any magnetic media, protect it with encryption as well as with media tracking technologies so that you know where it is and has been.
About the author:
Greg Schulz is founder of Server and StorageIO, an IT industry analyst consultancy firm and author of the books The Green and Virtual Data Center (CRC) and Resilient Storage Network (Elsevier). Learn more at www.storageio.com or on twitter@storageio.