Will the “Tape is Dead” Folks Please Sit Down?
A storage newsletter that shall go unnamed (we all make mistakes) discussed the dwindling of tape in 2012. Their opinion was that tape was on its way out. They pointed out that backup was moving to VTLs and that this change would be the death knell of tape.
The article granted archiving as a use case but questioned tape’s reliability over disk, and questioned tape’s slower access numbers over disk. Finally, the article reported that the only tape maker that was sharing numbers was SpectraLogic because news at other tape vendors was not good.
Everyone can have a bad day. From the perspective of 2014 here is why the article was largely wrong.
· Backup: They got this partially right. For decades tape was the backup medium of choice, and it is true that that is changing. Primary backup can be faster to disk or cheaper in the short-term to the cloud. The primary affected market is SMB, whose small amount of data can usually go straight to the cloud without impacting performance. However, mid-sized and enterprise produce reams of digital data that they must retain for long periods of time. For them, tape's density and economies of scale remain an excellent backup and/or archival choice.
· Dependability. Tape dependability did have a bad rep for a while, largely thanks to poor DLT generations. Yet with the growth and stabilization of the LTO standard, this is no longer the case. Tape is proving more reliable than disk, especially lower cost disk. The National Energy Research Scientific Computing Center (NERSC) reported that tape cartridges are up to four orders of magnitude more reliable than SATA.
There are several reasons for this, including the Bit Error Rate (BER) and the bit rot phenomenon. BER predicts the percentage of faulty bits per total number of written bits. Tape shows a 10x BER improvement over premium disk. Bit rot – the gradual decay of data stored on magnetic media – is also a real concern in long-term data storage. Both tape and disk are magnetic but spinning disk is at greater risk. (Thus the 15-30 year rated lifespan of LTO.)
· Sales: After showing signs of bottoming out a few years ago, 2013 sales stopped declining and 2014 is seeing sales rise. LTO mostly clearly describes the state of the tape market. LTO-6 drives have sold drives and media representing 100,000 PB-worth of data capacity on tape. LTO-4 is losing some ground as an older release, while LTO-5 sales are increasing. LTO-6 is selling even faster, aided by LTO's compatibility framework. Part of this popularity is cost-per-GB. Disk manufacturers are quick to cite falling disk prices but tape is still cheaper: a 1.5 TB tape cartridge costs about $40 compared to a similar capacity HDD for more than twice that.
· Performance. Disk-only vendors make statements like “tape is slower than disk.” That universal statement is not true: performance differs depending on the speed of the disk system or autoloader/library and the type of data being transferred. Disk is generally faster with random access where the disk heads can reach multiple specified locations faster than a tape drive can reposition its heads.
However, tape performance is generally superior with sequential access, which is why tape is particularly useful with backup, archive and big data sets.
Top Usage Cases for Tape Today
Today tape is thriving in important usage cases: archiving, the cloud (yes, the cloud), and big data. Disk manufacturers deny it but consider the source: vendors who do not offer tape products and thus have a vested interested in seeing tape die. These vendors will argue that they don't sell tape because they don't believe in tape. Yet in the face of tape’s capacity, economy and dependability, that is frankly disingenuous.
The largest archiving usage case for tape is long-term archival retention. The classic usage is long-term archival storage off-site, an exceptionally cost-effective storage solution. Active archiving is also a valuable use case, where tape offloads data sets from primary disk and keeps it immediately available for analytics and reloading onto the production system. Some software enables tape systems to natively host analytics.
For example, National Geographic’s NG Global Media manages massive media archives. Its Television MediaCore is a broadcast and post-production facility that provides media services to clients. They typically generate 5-10TB of content a day and archive a good 90% of it to Spectra Logic tape libraries. The archive stays immediately accessible since a significant percentage of the media is accessed and re-used a within very short time periods.