Tuesday, July 31, 2012

Three Numbers Presage A Crisis

Bill McKibben's Rolling Stone article "Global Warming's Terrifying New Math" is essential reading. The sub-head describes it:
Three simple numbers that add up to global catastrophe - and that make clear who the real enemy is.
Inspired by Bill, here are three numbers I've cited before that indicate we're heading for a crisis in digital storage:
  • According to IDC, the demand for storage is growing about 60%/year.
  • According to IHS iSuppli, the bit density on the platters of disk drives will grow about 20%/yr for the next 5 years. In the past, increases in bit density have led to corresponding drops in $/GB.
  • According to computereconomics.com, IT budgets in recent years have grown between 0%/year and 2%/year.
Something is going to give, and I doubt it will be the budget.

Tuesday, July 24, 2012

Storage Technology Replacement Policy

There's an anomaly in this graph from my prototype economic model of long-term storage. It shows the endowment as a multiple of the initial storage purchase cost that would have a 98% probability of not running out of money in 100 years, plotted against the Kryder rate, the annual percentage drop in storage purchase cost.

The region between Kryder rates of 25% and 35% is flat. It seems strange that, with storage prices dropping faster, the endowment needed isn't dropping too. I finally got time to figure out what is going on, and I now believe this is an artefact of the technology replacement policy model I implemented as part of the prototype model. It isn't that the policy model is unrealistic, although there is plenty of room for disagreement about alternative policies. Rather, the parameters I gave the policy model to generate this graph were unrealistic. Follow me below the fold for what Paul Krugman would call a wonkish explanation.

Thursday, July 19, 2012

Governments Rewriting History

Every so often I like to point to stories showing the importance, especially for government documents, of having multiple copies under independent, preferably somewhat antagonistic, administration as happened with the Federal Depository Library Program for paper, and as happens in the USDocs Private LOCKSS Network for digital documents. The reason is that governments are especially incapable of resisting the temptation, common to everyone, to edit history to make it less embarrassing. The great George Orwell understood this; Winston Smith's job in 1984 was rewriting history to make it conform to current ideology.

My latest example comes via Yves Smith's excellent blog, naked capitalism. She points to an article at Alternet by Thomas Ferguson, Paul Jorgenson and Jie Chen which describes how records of some major contributions to the 2007-8 election cycle have mysteriously vanished from the  Federal Election Commission's database of political contributions.
In 2008, however, a substantial number of contributions to such 501(c)s made it into the FEC database. For the agency quietly to remove them almost four years later with no public comment is scandalous. It flouts the agency’s legal mandate to track political money and mocks the whole spirit of what the FEC was set up to do. No less seriously, as legal challenges and public criticism of similar contributions in the 2012 election cycle rise to fever pitch, the FEC’s action wipes out one of the few sources of real evidence about how dark money works. Obviously, the unheralded purge also raises unsettling questions about what else might be going on with the database that scholars and journalists of every persuasion have always relied upon.
They write:
While you knew FEC data was unlikely to be the last word, you could be confident that whatever the agency did report was as true as it could make it. That the FEC would ever delete true reports of politically relevant money was literally unthinkable.
Other sources had made copies of the FEC data and added value:
Comprehending their formatting and correctly interpreting their myriad rows and columns required the patience of Job and the informal equivalent of a BS in computer science. As a consequence, most researchers threw up their hands. They didn’t directly use FEC data; instead they relied upon data reworked by some for-profit reseller, or more commonly, the Center for Responsive Politics.
The journalists were re-examining the FEC's database:
For the 2007-'08 election cycle, for example, we found millions of dollars in political contributions that appear to have escaped earlier nets. We are also able to do a much better job of aggregating contributions by large donors, which is key to understanding how the system really works.
What they found was:
We discovered the FEC deletions when cross-checking our results for big-ticket contributors. These deletions do not at all resemble other post-election corrections that the FEC routinely makes to its data downloads.
 They then give a series of examples of large donors whose contributions to the 2007-8 cycle have been whitewashed away.

The interesting and different thing about this public "naming and shaming" is that it had an effect. The very next day, the Alternet reporters found that at least some of the missing data had mysteriously re-appeared:
In mid-morning, certain reporters began tweeting that it was easy to find contributions that we specifically discussed on the FEC website. We checked one particularly famous name that we had also looked up only a few days before and found that he was indeed back.
The Tweeters who doubted the Alternet story were easily refuted because:
These downloads are public and dated, so anyone can verify what’s in them. The 2008 contribution by Harold Simmons that we mentioned is in the January download. It is not in the July 8 download. The same is true for other contributions we discussed to Let Freedom Ring by John Templesman, Jr., and Foster Friess. More broadly, the entire set of “C9” files covering 501(c)4 that we discussed is gone from the July download, with the trivial exception we mentioned. Needless to say, we checked the FEC’s database many times ourselves and we indicated that the original record of contributions by Simmons (and others) could still be found, if you knew exactly where to look.
The whole story, which was made possible by archiving copies of what the government was publishing when it was being published, seems to be having a happy ending. Except, perhaps, for the FEC. The credibility of the information they publish has been degraded, and will stay degraded until they come up with an explanation of what exactly happened and how they plan to make sure it never happens again. The FEC should look to Amazon for an example of how to make this kind of information public.

Tuesday, July 17, 2012

Storage roundup July 2012

From my continuing series on the dismal outlook for Kryder's Law, The Register reports on the continuing impact of the Thai floods:
Hard disk drive prices are unlikely to return to pre-flood levels until 2014 despite rising production levels, thanks to surging demand, vendor lock-in and a market dominated by just two suppliers, according to analysts.
Had there been no floods, and had the industry managed even just the 20%/yr increase in bit density that is now projected, and had margins remained stable instead of increasing dramatically, prices in 2014 would have been about 1/2 their pre-flood levels. So, three years later, costs will be at least double what would have been predicted before the floods.

More recent reports suggest that Western Digital is recovering somewhat better than was expected:
Keene said WD had "recovered" more quickly than industry commentators had forecast – the plants were nearing full capacity some months ago – and said only some high-spec products remained in tight supply.
while Seagate is having greater difficulty:
Seagate will miss its fourth quarter's sales target as its competitors recover faster than expected from floods that knackered hard drive supplies.
As part of a feature series on the solid state storage revolution, Ars Technica has a useful overview of the future of SSDs., with a clear explanation of why shrinking the flash cell size reduces not just the data retention time but also the number of write cycles a cell can sustain, and why moving from MLC (2 bits per cell) to TLC (3 bits per cell) makes the problems even worse. The article describes the contortions flash controller makers are going through to mitigate these problems, which are starting to sound like those the hard disk makers are struggling with. The article is suitably sceptical about the prospects for alternative solid state memories, but moderately enthusiastic about memristors. This is good news because:
a significant number of folks who have suffered through SSD failure have so suffered not because the flash wore out, but rather because of an actual component failure—a flash chip died, say, or the controller died. Component failure can occur in any device, and if memristor-based drives are eventually manufactured and assembled in the same plants by the same companies who make today's HDDs and SSDs—and we have every reason to believe they will be—then a memristor-based storage drive with a million-write endurance rating would likely be effectively immortal. Other components are likely to fail long before the storage medium reaches its write endurance limit.
The Register hits some of the same points and teases out some of the business implications:
There are several post-NAND technologies jostling for prominence, such as Phase-change memory, resistive RAM, memristors and IBM's Racetrack memory. All promise greater capacity, higher speed and longer endurance than flash. It's not clear which one of them will become the non-volatile memory follow-on from NAND, but, whichever it is, the controller software crafter to cope with NAND inadequacies won't be needed.
MLC NAND wear-levelling and write amplification reduction technology won't be needed. The NAND signal processing may be irrelevant. Garbage collection could be completely different. Entire code stacks will need to be re-written. All the flash array and hybrid flash/disk startups will find their software IP devalued and their business models at risk from post-NAND startup's IP with products offering longer life and faster-performance.
One solid state storage technology wasn't included in these reviews because it was only announced July 10. Karlsruhe Institute of Technology managed to build a memristor-like 1-bit device using only 51 atoms:
They point out that a bit on a hard disk drive uses about 3 million atoms while their molecule has just 51 atoms inside it, including the single iron atom they've inserted at its centre. Wow, that's 58,823.5 times denser, say 50,000X for argument's sake, which would mean a 4TB hard drive could store 200PB using molecular bit storage.  - except that it couldn't ... If molecular bit storage is ever going to be used, it will be in solid state storage and you will still need to access the bits – with one wire to deliver the electric pulse to set them and another wire to sense their setting. Even using nanowires, more space in the device would be taken up by circuitry than by storage.
At Slashdot, Lucas123 describes how hybrid drives, the compromise between SSDs and hard disks, which add a small amount of solid state storage to a normal hard drive, do not in fact deliver the advantages of both with the disadvantages of neither and so are not succeeding in the market:
New numbers show hybrid drives, which combine NAND flash with spinning disk, will double in sales from 1 million to 2 million units this year. Unfortunately for Seagate — the only manufacturer of hybrids — solid-state drive sales are expected to hit 18 million units this year and 69 million by 2016. ... If hybrid drives are to have a chance at surviving, more manufacturers will need to produce them, and they'll need to come in thinner form factors to fit today's ultrabook laptops.
The Register reports on a briefing on disk technology futures from Western Digital, which repeated Dave Anderson of Seagate's (PDF) 2009 point that there is no feasible alternative to disks in the medium term:

The demand for HDD capacity continues unabated as there is no alternative whatsoever for fast access to online data; NAND flash fabs are in short supply and have a long lead time. In 2011, 70 per cent of all the shipped petabytes were HDDs, with optical, tape, NAND and DRAM making up the rest. Some 350,000PB of disk were shipped, compared to about 20,000 PB of NAND.

WD's COO, Tim Leyden, reckons another 40 NAND fabs would be needed to make 350K PB of NAND, and that would cost $400bn at $10bn/fab capable of shipping 8.8K PB/year. It isn't going to happen any time soon.
Here is WD's version of the Kryder's Law curve, on a scale that minimises the slowing from 40%/yr to 20%/yr in the last few years, and they play that down as temporary in words too:
WD says that HDD areal density growth has slowed from an annual 40 per cent compound annual growth rate to just 20 per cent as the current PMR recording technology nears its maximum efficacy, with a transition to energy-assisted magnetic recording (EAMR) coming and representing the possibility of regaining the 40 per cent rate.
But they are clearly concerned enough to raise the possibility of adding platters (and thus cost):
Our contact said that 5-platter 3.5-inch drives were a possibility.

With a trend towards thin and light drives for Ultrabooks, the possibility of platter addition is denied in this market sector.
The decreasing proportion of the market occupied by PCs that use 3.5" drives is clear from this graph from Forester Research. The competition is not just laptops, netbooks and tablets but also smartphones:
Vendors shipped close to 489 million smartphones in 2011, compared to 415 million PCs. Smartphone shipments increased by 63% over the previous year, compared to 15% growth in PC shipments.

Canalys includes pad or tablet computers in its PC category calculation, and this was the growth area in PCs. Pad shipments grew by 274% over the past year. Pads accounted for 15% of all client PC shipments.  Desktops grew by only two percent over the past year, and notebooks by seven percent.
Finally, on June 29th at the height of the "derecho" storm affecting the DC area, Amazon's cloud suffered an outage:
An Amazon Web Services data center in northern Virginia lost power Friday night during an electrical storm, causing downtime for numerous customers — including Netflix, which uses an architecture designed to route around problems at a single availability zone. The same data center suffered a power outage two weeks ago and had connectivity problems earlier on Friday.
Many of Amazon's customers were impacted:
Netflix, Pinterest, Instagram, and Heroku, which run their services atop Amazon's infrastructure cloud, all reported outages because of the power failure.
Amazon produced their characteristically informative post-mortem on the event, which explained the cause:
At 7:24pm PDT, a large voltage spike was experienced by the electrical switching equipment in two of the US East-1 datacenters supporting a single Availability Zone. ... In one of the datacenters, the transfer completed without incident. In the other, the generators started successfully, but each generator independently failed to provide stable voltage as they were brought into service. ... servers operated without interruption during this period on the Uninterruptable Power Supply (“UPS”) units. Shortly thereafter, utility power was restored ... The utility power in the Region failed a second time at 7:57pm PDT. Again, all rooms of this one facility failed to successfully transfer to generator power ... all servers continued to operate normally on ... UPS ... power. ... the UPS systems were depleting and servers began losing power at 8:04pm PDT. Ten minutes later, the backup generator power was stabilized, the UPSs were restarted, and power started to be restored by 8:14pm PDT. At 8:24pm PDT, the full facility had power to all racks. ... Approximately 7% of the EC2 instances in the US-EAST-1 Region were ... impacted by the power loss. ... The vast majority of these instances came back online between 11:15pm PDT and just after midnight. Time for the completion of this recovery was extended by a bottleneck in our server booting process. ... The majority of EBS servers had been brought up by 12:25am PDT on Saturday. ... By 2:45am PDT, 90% of outstanding volumes had been turned over to customers. We have identified several areas in the recovery process that we will further optimize to improve the speed of processing recovered volumes.
They also provided detailed descriptions of the mechanisms that caused the customer impacts, which should be required reading for anyone building reliable services.

Thursday, July 12, 2012

Preservation as a Cloud Service

I'm not the only one commenting on the "affordable cloud storage" hype that Tesella seems to have swallowed whole as they announce Preservica, their "preservation as a service" competitor for DuraCloud. Via The Register, we find Nati Shalom of Gigaspaces making the fundamental point about cloud economics:
Many people think that cloud economics starts to pay dividends immediately when you move to an on-demand usage model, paying only for what you use. Cloud can actually be fairly expensive when hosting environments in use are not elastic. I was surprised to see how many startups and SaaS organizations still run their applications in the cloud just as they would in any static hosting environment. While the pay-per-use model has a lot of promise for cost-savings if our applications aren’t designed for elasticity the cost of running the application in the cloud may end up costing you more. Most of the mission-critical applications have not been designed for elasticity and on-demand usage.
The flaw in the concept of DuraSpace, Preservica and other preservation in the cloud ideas is that digital preservation is the canonical example of a mission-critical application not "designed for elasticity and on-demand usage". The business models of cloud service providers base pricing on the value to their customers of eliminating the over-provisioning needed to cope with peak demand. Digital preservation is a base-load application, it doesn't have peaks and troughs in demand that require over-provisioning.

Matt Asay makes the same point:
But the overall driver of cloud computing, at least for now, is business agility. The early adopters driving cloud computing don't need discounts, because cost isn't their primary motivation. Help them figure out how to do more, faster, and the cost equation of public versus private clouds becomes somewhat of a non-issue.
Again, does anyone think the primary need for digital preservation is agility?