Speed (n.) Swiftness. Rapidity. Rate of motion or performance. (from Merriam Webster)
A trade show participant once told me he didn’t use tape because, “…it wasn’t fast enough”. When asked how fast he needed to move data he said he needed to move it at about 200 MB/s for his backup purposes. Furthermore, he believed only disk was fast enough to deliver. When told a single LTO-4 tape drive could stream data at 120 MB/s and only 2 drives were needed to meet his requirement, he was shocked. Unfortunately, his perception of tape is not exceptional given the marketing dollars spent “educating the masses” about the speed of disk versus tape.
So what is it about tape’s speed that storage buyers are missing? If one looks only at random seek time, critical within on-line transaction processing environments for instance, then tape is indeed slower than disk. But that’s not the only performance metric that’s important.
Raw throughput can be a requirement in big data environments when moving huge files quickly from storage to application for processing. Today’s tape drives are built to deliver speed in these areas. For instance, LTO-5 tape drives move data at 280 MB/s compressed while enterprise tape drives from IBM are capable of slinging data around at 360 to 650+ MB/s compressed respectively. This means it’s possible to reach transfer rates of upwards of 1PB per hour given today’s enterprise library configurations. Believe it or not, there are HPC users currently pushing requirements for 1PB per hour data rates. Tape can deliver that kind of speed on that kind of scale.
When it comes to transporting data between sites, the performance of physical tape movement becomes really interesting. For example, electronically moving 10 TB of data via an OC-3 or OC-12 line can be expensive running from $10,000 to well over $100,000 per month respectively. At these prices you have the distinct privilege of transporting that data in 6.1 days for an OC-3 and 1.5 days for an OC-12. In contrast, you can put 10 TB of data on 2-4 tapes, depending on the type, drop them into a FedEx box and ship them overnight at a cost that’s little more than a rounding error relative to that of the cost of the digital pipes. In other words, you can’t overestimate the bandwidth of a truck full of tapes – especially for the price!
Will you always have to move data this fast? Maybe not, but when you do, tape can help you do it at a fraction of the cost of the alternatives. Maybe that’s why tape rolls on.
To learn more about Why Tape Rolls On, see part 2 of this series discussing the Green Storage characteristics of tape.