Redundant Array of Independent Tape
And that innate advantage may be intensified thanks to a system of deploying tape that is now being deployed in some intensive high performance installations such as the US Oak Ridge National Computing Laboratory. Although these are not yet mainstream, in the future, the amount of data and throughput being discussed will filter down into midrange applications, just as surely as Formula One technology eventually finds its way into the mass-automobile market. This advanced tape system is called RAIT, Redundant Array of Independent Tape.
RAIT improves the throughput of large sequential files by creating multiple parallel data streams into the tape subsystem and, as with RAID, it can also provide various degrees of fault tolerance for higher availability.
RAIT levels are implemented through software, depending on the number of tape drives in the array configuration; how critical drive recovery is in the event of a fault; and how vital it is to maximise tape throughput. The data transfer rate is limited to the slowest drive in the stripe although ideally all RAIT drives will be of the same generation - e.g. all LTO-6, all LTO-7. As with RAID, RAIT can offer data redundancy without needing to create multiple copies. Striping and parity are the keys to RAID and RAIT implementations.
With RAIT data striping, data is distributed over multiple tape devices, so that the data blocks are processed in parallel and sent to tapes in multiple drives simultaneously. This dramatically increases throughput. Meanwhile, all of these physical striped drives are virtualised so as to appear as a single drive. A RAIT stripe can extend to up to 16 drives depending on the software used, just like sixteen lanes of vehicles on a physical highway.
Tape’s advantages for building the archive superhighway
To summarise, if we assume that access to all of the data, all of the time, is the fundamental requirement, it’s likely that a private cloud will be more convenient than tape or the public cloud. But such convenience comes at a price since the acquisition cost of an object storage system will be several times more expensive than the equivalent capacity stored on tape for the server utilisation and redundancy reasons mentioned above.
And such expensive convenience may not be a pre-requisite for the application anyway. For very large active archives, it may make most sense to use tape and private cloud in combination: an object storage solution in the front end of a system, underpinned by vast quantities of cheap, offline LTO tape, where data is moved for analysis or retrieval between different platforms as business needs dictate, using supercharged innovations like RAIT.
Incidentally, this is the principle behind hierarchical archive management solutions like HPE’s Data Management Framework. The automated functionality of HPE DMF allows efficient utilisation of storage infrastructure by removing stale data from defined data tiers and provides a virtual storage space that appears to be unlimited in size. Important data is automatically retrieved as needed, making storage look ”bigger on the inside“…..but already I’m pushing the limit of your coffee break! The HPE DMF is another interesting and exciting topic for another day (but if you want more information, you will find it here!)