Brewster Kahle's "Distributed Web" proposal

Back in August last year Brewster Kahle posted Locking the Web Open: A Call for a Distributed Web. It consisted of an analysis of the problems of the current Web, a set of requirements for a future Web that wouldn't have those problems, and a list of pieces of current technology that he suggested could be assembled into a working if simplified implementation of those requirements layered on top of the current Web. I meant to blog about it at the time, but I was busy finishing my report on emulation.

Last November, Brewster gave the EE380 lecture on this topic (video from YouTube or Stanford), reminding me that I needed to write about it. I still didn't find time to write a post. On 8^th June, Brewster, Vint Cerf and Cory Doctorow are to keynote a Decentralized Web Summit. I encourage you to attend. Unfortunately, I won't be able to, and this has finally forced me to write up my take on this proposal. Follow me below the fold for a brief discussion; I hope to write a more detailed post soon.

The Curious Case of the Outsourced CA

I took part in the Digital Preservation of Federal Information Summit, a pre-meeting of the CNI Spring Membership Meeting. Preservation of government information is a topic that the LOCKSS Program has been concerned with for a long time; my first post on the topic was nine years ago. In the second part of the discussion I had to retract a proposal I made in the first part that had seemed obvious. The reasons why the obvious was in fact wrong are interesting. The explanation is below the fold.

The Amazon Tax

Ben Thompson at Stratechery has an insightful post entitled The Amazon Tax on the 10^th anniversary of the rollout of Amazon S3:

Until then Amazon Web Services had primarily been about providing developers with a way to tap into the Amazon retail store; S3, though, had nothing at all to do with retail,² at least not directly.

Below the fold, some comments.

Following Up On The Emulation Report

A meeting was held at the Mellon Foundation to follow up on my report Emulation and Virtualization as Preservation Strategies. I was asked to provide a brief introduction to get discussion going. The discussions were confidential, but below the fold is an edited text of my introduction with links to the sources.

Long Tien Nguyen & Alan Kay's "Cuneiform" System

Jason Scott points me to Long Tien Nguyen and Alan Kay's paper from last October entitled The Cuneiform Tablets of 2015. It describes what is in effect a better implementation of Raymond Lorie's Universal Virtual Computer. They attribute the failure of the UVC to its complexity:

They tried to make the most general virtual machine they could think of, one that could easily emulate all known real computer architectures easily. The resulting design has a segmented memory model, bit-addressable memory, and an unlimited number of registers of unlimited bit length. This Universal Virtual Computer requires several dozen pages to be completely specified and explained, and requires far more than an afternoon (probably several weeks) to be completely implemented.

They are correct that the UVC was too complicated, but the reasons why it was a failure are far more fundamental and, alas, apply equally to Chifir, the much simpler virtual machine they describe. Below the fold, I set out these reasons.

The Dawn of DAWN?

At the 2009 SOSP David Anderson and co-authors from C-MU presented FAWN, the Fast Array of Wimpy Nodes. It inspired me to suggest, in my 2010 JCDL keynote, that the cost savings FAWN realized without performance penalty by distributing computation across a very large number of very low-power nodes might also apply to storage.

The following year Ian Adams and Ethan Miller of UC Santa Cruz's Storage Systems Research Center and I looked at this possibility more closely in a Technical Report entitled Using Storage Class Memory for Archives with DAWN, a Durable Array of Wimpy Nodes. We showed that it was indeed plausible that, even at then current flash prices, the total cost of ownership over the long term of a storage system built from very low-power system-on-chip technology and flash memory would be competitive with disk while providing high performance and enabling self-healing.

Although flash remains more expensive than hard disk, since 2011 the gap has narrowed from a factor of about 12 to about 6. Pure Storage recently announced FlashBlade, an object storage fabric composed of large numbers of blades, each equipped with:

• Compute – 8-core Xeon system-on-a-chip – and Elastic Fabric Connector for external, off-blade, 40GbitE networking,
• Storage – NAND storage with 8TB or 52TB raw capacity of raw capacity and on-board NV-RAM with a super-capacitor-backed write buffer plus a pair of ARM CPU cores and an FPGA,
• On-blade networking – PCIe card to link compute and storage cards via a proprietary protocol.

Chris Mellor at The Register has details and two commentaries.

FlashBlade clearly isn't DAWN. Each blade is much bigger, much more powerful and much more expensive than a DAWN node. No-one could call a node with an 8-core Xeon, 2 ARMs, and 52TB of flash "wimpy", and it'll clearly be too expensive for long-term bulk storage. But it is a big step in the direction of the DAWN architecture.

DAWN exploits two separate sets of synergies:

• Like FlashBlade, it moves the computation to where the data is, rather then moving the data to where the computation is, reducing both latency and power consumption. The further data moves on wires from the storage medium, the more power and time it takes. This is why Berkeley's Aspire project's architecture is based on optical interconnect technology, which when it becomes mainstream will be both faster and lower-power than wires. In the meantime, we have to use wires.
• Unlike FlashBlade, it divides the object storage fabric into a much larger number of much smaller nodes, implemented using the very low-power ARM chips used in cellphones. Because the power a CPU needs tends to grow faster than linearly with performance, the additional parallelism provides comparable performance at lower power.

So FlashBlade currently exploits only one of the two sets of synergies. But once Pure Storage has deployed this architecture in its current relatively high-cost and high-power technology, re-implementing it in lower-cost, lower-power technology should be easy and non-disruptive. They have done the harder of the two parts.

Dr. Pangloss loves technology roadmaps

Its nearly three years since we last saw the renowned Dr. Pangloss chuckling with glee at the storage industry's roadmaps. But last week he was browsing Slashdot and found something much to his taste. Below the fold, an explanation of what the good Doctor enjoyed so much.