Is Optical Disc an Illusion?
Facebook made a big splash a year or so back by launching a project to showcase archiving on Blu-ray optical disc. It developed a 10,000 Blu-ray disc system that can hold a PB. The intention was for it to act as an archive system for the millions of photos and videos uploaded onto the site. These items can’t be discarded yet most might never be accessed for years, if ever again. So the optical disc system acts as cold storage and is said to be 50% cheaper than using hard disk drives (HDD) and 80% more energy efficient.
While Sony bought the startup that was spun off from this Facebook research in an effort to stimulate this market, many are dubious of its staying power. Aaron Ogus, Partner Development Manager at Microsoft Azure, questions the math of companies like Facebook and Google who are buying servers or advocating optical disc yet their real business is selling ads.
“When you buy data centers, generators, networks and servers but sell ads, you might not know what things cost,” said Ogus. “Optical struggles on capacity; one optical disc isn’t expected to reach a capacity of 1 TB by 2020.”
Fred Moore, an analyst at Horison Information Strategies, laid out the technical side of the Blu-ray specification: Single-layer Blu-ray is up to 25GB/layer while dual-layer discs have up to 50GB/layer; new Ultra HD Blu-ray discs will hold 66GB and 100GBs; 300GB to 1TB multi-layer discs are planned; the read rate is only 17.1 MB/sec; and its reliability rate is below that of all other magnetic devices (tape and HDD). However, the Write Once Read Many (WORM) format is more reliable than discs that can be repeatedly read and written to.
“Optical disc has fallen far behind magnetic storage in capacity, performance and reliability,” said Moore. “It is not cost-effective for data center usage.”
Tom Coughlin, an analyst at Coughlin Associates, agreed that optical lacks the necessary media capacity. But he pointed out that it provides a faster access time than tape so may have a value proposition for some forms of archiving.
“Optical is faster to access but has much lower capacity,” he said.
He foresaw a storage tiering arrangement coming into play where the HDD operated for data that required reasonably fast access, supported by cheaper optical disc for faster access/low capacity then and tape for higher capacity/slower access.
Another big challenge facing the optical industry is that the industry is losing its large consumer base from DVD sales. This is a phenomenon that affects all forms of media at some point in their lifecycle. After punch cards vanished, tape ruled for decades. It also found its way into consumer products such as cassettes and video cartridges. But the CD and DVD gradually eroded that market and the consumer tape market has vanished. This led to some tough years for the tape industry and it struggled to remain relevant and began to lose to HDD within the enterprise as a backup medium.
The same thing is now happening with all forms of disk. The HDD market is dwindling as covered above, the music CD market lost out to music downloads and the DVD, too, is about to fade from memory as online streaming takes over.
“The lack of that revenue stream will inhibit research into optical tape,” said Coughlin.
One vendor that tried to make optical work is Spectra Logic. CEO Nathan Thompson said his company largely leaves top tier, fast storage to others. It is interested, he said, on the bottom 80% of rarely accessed data, which he calls deep storage. Accordingly, the company experimented with a 15,000 optical disc robot design with 50-year media life for write-once storage. This was based on the fact that optical and HDD are cheaper than tape for lower capacities. Per his research, this holds true to about 2 PB or so.
“Once you get above that, tape can hold more and will cost six times less for very high capacity,” said Thompson. “The more capacity you add, the bigger the gap.”
Spectra Logic, therefore, has since shelved that project to focus on tape as the repository for deep storage. Instead, it has just released a Shingled Magnetic Recording (SMR) hybrid HDD and tape product called ArcticBlue.
So Facebook and Sony aside, few vendors seem willing to put much faith in optical for the long haul.
Ed Childers, Senior Technical Member at IBM, predicted the eventual decline and fall of the optical disc as any kind of archiving medium.
“Optical is getting squeezed out and it is not scaling in terms of density,” said Childers.
Moore agrees. Its heyday will probably be remembered as that brief period of Blu-ray and DVD dominance. But it failed to make the grade in the enterprise.
“Blu-ray disc set the standard for high definition picture and audio quality,” said Moore. “It was popular in the home and car, but never in the data center.”