Bitcoin chain storage using database engine is putting high stress on the flash storage media (SD, USB, etc.) in terms of wear and tear. It is close to worst possible access pattern: write-ahead-logging causes many rewrites with almost no reads. Cheaper flash media would fail before you complete the whole blockchain synchronization.

The same thing was tried by somebody else on cheap Dell laptops with cheap SSD in the days when the main blockchain database was still Berkeley DB. They would reproducibly permanently fail during initial synchronization. The current LevelDB is less bad than BerkeleyDB, but still far from being flash-optimized.

To be really reliable you would need two separate hardware storage pieces: one for the main OS and important files like wallet.dat and one for constantly rewritten data that is really throwaway: blockchain storage and log files.

Edit: One thing that I forgot about: many SD card media have controllers that are internally optimized for FAT or exFAT file systems and don't perform well when formatted with NTFS. NTFS security and reliability features are pointless for blockchain storage. This is one more reason to have split devices when specifying cheap flash storage media.

Well, Bitfury (corporation) and Punin (person) promised to release the specifications for their communication controller/level shifter/differential transceiver chip.

Bitfury Designs released under CC-BY-SA

https://bitcointalk.org/index.php?topic=1360038.0

Maybe sidehack has some information in English now? I vaguely remember seeing some posts in Russian that are now deleted, and I'm only quarter-literate in Russian.

No coin miner is ever standard. The main fun is that they invalidate all standard design flows: they either lead to failure or vast over-specification and under-performance.
As far as I know several people tried to use the internal self-clocking and reported problems with them: not always starting reliably and humongous jitter. My experience (not with mining, but with somewhat similar digital-but-nearly-analog chips) is that you are better off forcing your own external clocking and very frequently run short test mining jobs with known answers (like once every second feed the chip a job that requires just a few increments to find the golden nonce).
This is where I disagree with you the most. The failure modes of MOS devices are really strange, silicon has negative temperature coefficient and is prone to creating hot spots, where the device fails way below their normal rated specifications when the dI/dt or dV/dt was too fast. Hopefully you'll get your 55nm Bitfurries really cheap so you won't regret skimping on the safeties. But speccing and acknowledging the need for parallel transil is a good start.

My school had a program sponsored by International Rectifier (www.irf.com), we could burn power semiconductors for free (provided that we documented the conditions of the burn) and I still have some fond memories from that time.

I've seen your "back of the envelope" calculations and basically I suggest that you get a bigger envelope and make some more calculations. In particular, don't always assume that Vpeak/Vrms = 1.4, it varies widely with the load.

Or maybe just want want to go for the shock value and use one farad capacitors in your ripple filter, the ones that are used by the bass-heavy car audio enthusiasts. 

Yeah, it will most certainly work, when designed correctly. I'm still perplexed why you were concerned about few percentage point of RMS voltage variation (220-235V or 205-265V) while your main concerns should be ripple and protection against spikes.

Ripple itself on a single-phase system would be around 40% (25%-50% if I remember correctly) unless you drastically over-design the ripple filter and your rectifier diodes conduct only during few percents of the mains cycle. I'm unclear what is the purpose of your design: (1) show that it is possible using ridiculous over-specification or (2) an experiment in a proper power electronics design that could be practically scaled up and deployed later.

In case (1) you just don't worry about inductive spikes in the mains voltage because you ridiculously over-specified capacitors.

In case (2) you have to have proper protection against spikes. I don't have specific information about Bitfury's chips, but in metal-insulator-semiconductor chips the over-current protection is typically not enough. The breakdown is not only thermal, it involves electromigration of metal over insulator and insulator under metal. Electromigration is both irreversible and cumulative. In normal industrial practice you will need parallel over-voltage shunt to extinguish the inductive spikes coming from the mains. Relying on over-current protection is only acceptable for bipolar-junction devices where the junction breakdown is reversible and non-cumulative.

In case (1) you just don't worry about power factor and accept that the diodes conduct only during top few percents of a cycle.

In case (2) you'll have to use 3-phase power and polyphase rectifier design to have acceptable power factor and diodes that conduct current around 60 degrees of the 360 degrees cycle.

Again, I don't have a specific knowledge about Bitfury's chips and their communication protocols, but some power electronics designs deal with 100% ripple by resetting the devices at 100Hz or 120Hz during the zero-crossings of the mains power. It probably wouldn't pertain to Bitfurries, but you still may consider modulating your mining clock rate during each half-cycle of the ripple. Over-clock when the chip are over-volted on the average and under-clock when the chips are under-volted on the average. The required additional power in the controller is next to nothing when compared with the power losses in the full, actively stabilizing regulators. Adjusting the clock rate several hundred times per second shouldn't be a problem for properly designed controller.

I'm sorry my first response took you for a noob. I simply didn't consider the case of (1), a design like one would do to settle a bet. In the past I had to deal with many people who were digital design experts but relatively ignorant in power electronics design. They would advocate type (2) designs with flaws obvious to anyone who had to experience beyond stabilized/regulated benchtop power supplies.

I don't think that you understand how a rectifier works. 220V is an RMS voltage (root mean square). This means that unloaded bridge rectifier produces on output 220 * sqrt(2) or about 311V. The output under load will be lower depending on the exact design of your ripple filter.

You need to actively monitor angle of conduction in the rectifier to operate you mining string safely. This means that you can't use diodes in the rectifier but SCRs (thyristors) and actively control when to turn them on in each cycle (not difficult at 50Hz or 60Hz). For experiments (to learn) you can use diodes in the rectifier and an artificial resistive load (like incandescent light bulbs) in parallel with your string of chips.

Have fun!

Edit: In practice people using unregulated rectifiers use multi-phase rectifiers (typically 3 or 6 phases), not a single phase rectifiers. See comments about rectifiers in https://en.wikipedia.org/wiki/Polyphase_system .

Edit2: For fun (to play and learn) use a welding rectifier (with a transformer or an auto-transformer) for testing. Just remember to disable the arc-start circuitry, the one that briefly produces higher output voltage to make it easier to spark the arc for welding. You will need less chips in your string.

Thank you for your suggestion. I had the firewall set for logging only blocked connection attempts. I enabled logging of the successful IPv6 connections and I see 2a01:4f8:212:3b1f::2 as the source address. So the connections are coming from the same monitoring server. They are kept open for exactly one minute and one second.

Do you happen to find the URL for seeing the testnet results?

I'm not sure if Addy Yeow is still following this thread, but I noticed an important change.

My Bitcoin testnet nodes started getting incoming connections from clients calling themselves /bitnodes.21.co/ .

This is a standard signature that was used on Bitcoin mainnet monitoring tools available via https://bitnodes.21.co/ .

Does anyone know the URL to access the equivalent testnet website?

I'm going to move/repost something I wrote several months ago in regards to coin mining in London, UK. My original post was in the thread related to the then new Bitmain miner and didn't gather any responses because it happened to be far off the main topic of that thread. Maybe here in this thread we will get better discussion going?

---

I don't know anything about this particular company. But I do happen to have some fresh information about the real-estate/property developers in Greater London area. There is plenty of freshly build/renovated residential and commercial locations that are looking for a buyer without any current tenants. Developers are again resorting to having fake occupancy by letting trustable people to live and use the facilities free of rent&utilities. Conditions typically are: be personally known to trusted people in the construction business, be able to move out on a very short notice (few days at most), be trusted and capable of leaving the property in the "as new" condition, don't look and behave like a chav.

The holy grail of the Bitcoin mining is free electricity. Paradoxically, it is easiest to get it in the areas that normally have very high rents and costs of utilities. You won't get it on the regular commercial/residential terms, only as a temporary fallback financed by the developers/bond holders/speculators. Certainly, you won't find them advertised anywhere.

From my broader experience I'm pretty sure that such conditions aren't limited to London, UK. So keep your eyes open for opportunities like that in the city near you.

Again, the above was a general information, not specific to any particular offer discussed above.

---

In the months passing since then I have one more data point: certain woman artist moved her ceramic workshop from far-our rural England to rather prestigious London location, including rather large custom electric kiln. She had lowered her monthly expenses taking advantage of the promotional deal offered by the property developer management. Obviously art studio isn't industrial-size coin mining, but is quite close as far as practical incidentals.

The question is "How could you tell if they did or did not successfully deploy it?" Can you just trust their say so? The current official Litecoin client has defect/problems/bugs related to network and hash-power splits. The Litecoin Core development group doesn't seem to be really interested into looking to this problem.

Anyone who already has a working Litecoin client can just quickly run a second copy on the testnet, just start it with a "-testnet=1" flag. The required disk space is just over 1GB and the bandwidth load is minuscule. There's enough seed nodes to download it quickly, but the problems of not propagating transactions and newly mined blocks will be obvious. It isn't like to reproduce the problem one needs some sort of complex environment. Just start a copy and wait till it hangs while having many open connections. To speed up the bug reproduction one could simply shut it down cleanly after downloading couple of months of blockchain and then try restarting the synchronization. The bug (or bugs) are very obvious and not hard to reproduce.

Likewise, to see the mining hash-power split one doesn't need dedicated Litecoin ASIC mining hardware. Even a single core on a multi-core CPU could theoretically produce blocks at the expected rate of about 2-3 minutes. But they just won't propagate as the most peer to peer connections get stuck in open state but "UNKNOWN" sync height.

Personally, I have doubts that you (plural 'you') will be able to deploy it successfully.

I'm basing this on my observation of Litecoin's testnet. It has again split into many different branches despite all of them using the original, unmodified, official Litecoin code. Nearly all nodes run 0.10.*, with majority at 0.10.4. The last major split of this type happened just before Christmas, at a height of 1013820. Right now the nearest one can get to 'official' main branch is at 1013879. The testnet hash rate stands at pitiful 152 H/s, yes, just over one hundred hashes per second.

I always espouses the opinion that the general traffic level and health on the testnet are a good indicators of the future health and traffic levels on the mainnet. Less than hundred blocks were mined over the holiday period on the testnet. What this really means is that nobody is doing any significant development, testing or deployment of the new Litecoin-related software and businesses. Even a single core decade old Intel/AMD CPU can sustain over 1 kilohash per second.

The problem of testnet splitting was reported here by me in the past and surely many more people are aware of it. The last time the Litecoin core developers simply decided to mask it by deploying a simple hidden mining pool backed by the ASIC miner. It wasn't a real solution to the propagation bugs, but at least masked them well enough to allow resumption of global Litecoin testnet operation. But the underlying bug clearly wasn't fixed since 0.10.2.2 days which anyone can observe today.

That "very soon" cannot be taken as a serious promise from a developer.

Did you try using "-connect" to force talking to just one peer?

I haven't tried 0.13.1, but with some older versions that resulted in "reproducible ordering", I don't recall if it was "natural order".

This looks like a real opportunity for some scam artist to earn serious consulting fees.

Last century, when I was still working in the entertainment business we one prospective investor like that. He was a son of the owner of a chain of used car lots that catered primarily to Spanish speakers in southwestern USA. He wanted to start a rap label catering to non-English speakers. I don't recall the actual money invested wasted, but it was in the range between $1M and $100M. It was completely integrated, it had A&R scouts, recording studio, duplicating plants and marketing organization. All went to waste because none of it sold, although some of the artists they signed were later successful under new names and new management.

I haven't personally met the guy, but I read his e-mail and spoke with many of his "advisers" and "assistants". The lack of though and introspection is very similar. It is an opportunity for e.g. newly minted lawyer who needs to pay of his school loans. He won't pocket the whole money but will nicely earn during buildup and inevitable liquidation.

The guys I used to know got a lot of free limousine rides out of the above "deal". If this guy is real then be prepared to ride some uncomfortable but very fast cars.

No kidding, this looks like a real opportunity for some smooth, but ruthless operator who doesn't mind having to do some butt kissing when it handsomely pays. Just lawyer up appropriately, those kinds of scams aren't prosecuted in the USA because they involve "accredited investors."

Edit: Along with kissing butt, you will probably need to kick butt. Feel free to abuse me verbally as a "naysayer", "banker's stooge", "statist", etc. I don't mind. It is part of the entertainment in the front row.

Danny's list started as a list of people whose arguments he couldn't refute, so he started advocating ignoring them as a signature spammers. The best example is MPOE-PR who never participated in any paid signature campaign but mercilessly  and very skillfully poked fun at some of Danny's arguments. Anyone ignoring MPOE-PR would miss some of the best satirical and critical writing on Bitcointalk, although the account is no longer active.

The list also includes me and several other long time members who had poked fun at Danny and other former stalwarts turned later scammers like DeathAndTaxes.

The list may be statistically correct, i.e. the majority of the names on the list are or were wearing paid signatures and spamming them. But the list also includes multiple people involved in scam busting. And therefore becomes a danger to the newcomers who won't be able to see the warning and explanations of the old scams.

About the latter additions I have nothing to say, neither positive or negative, I wasn't really paying attention. I'm mostly interested in scams not spam.

Conceptually your ring of 4 peers looks correct and should be capable of mining. I don't know why it isn't working for you.

The only thing I can suggest is to search the net for the phase "testnet in a box". There are multiple pages describing exactly how they did it. Just retrace exactly their steps. I've done it multiple times, but my computers used for testing are in storage and I can't look at them now.

For the Bitcoin Core client to start mining it requires some minimal rudimentary peer to peer network. If I remember correctly the minimum is either 2 or 3 peers. You actually don't need the separate computers, the necessary peer to peer network can be created on a single computer by running multiple Bitcoin Core instances under multiple user accounts.

I don't remember the details, you'll have to experiment with starting multiple instances of Bitcoin Core with several flags: -connect=? , -port=? and -rpcport=? .

Edit: If I remember correctly such setup is not called "offline mining", it is called "testnet in a box", even if you aren't running testnet.

Also, research older versions of cgminer that still supported GPU mining of Bitcoin to use for your tests. GPU mining is much more power-efficient than CPU mining. With a mid-range laptop (couple of years ago, when GPU mining of Bitcoin was still a thing) you should be able to run all the required programs (multiple instances of Bitcoin Core and at least one instance of cgminer) on batteries and without spinning up the laptop's fan or having to suffer a hot laptop. Even if you work on a desktop and not on the laptop, the power savings and the fan noise reduction are really helpful for the developer.

Yes, not a line, but a reference.

When you move a $20 bill from your left pocket to your right pocket do you consider that a transaction?

When you pay for a $3 pumpkin spice latte with a $20 bill what is the transacted volume?

Yep, my nose can sniff pre-crime before the criminal can even conceive the details of the future crime. 

And I don't live in a pool of physiological salt solution. 

The case MtGox vs. Dwolla wasn't about stealing bitcoins, it was about stealing dollars. They had some sort of net-transfer agreement to needlessly transferring dollars back and forth. The reports/invoices used in those bank transfers were created using bogus harvesting algorithms. The bogusness wasn't complete, it sums in the spreadsheets were close enough to real ones that the respective CEOs/CFOs signed them off as "true and accurate under the penalty of perjury". I don't remember further details, they were briefly described in some exhibits to that lawsuit.

Ask yourself a question: you were planning on computing some sort of "transaction volume" aggregate. The bugs that allowed to distinguish "payment" output from "change" output were fixed years ago, when Hal Finney was still alive. So what were you planing on doing to truthfully compute that in 2016?

This is the reality of the Bitcoin milieu. There are many people coming to this board with request of supporting strange combinations of tools. Frequently this is because Bitcoin's (near-)immutability has created a problem with somebody's preexisting fraud or scam.

In my memory the most visible case of importing Bitcoin data to Microsoft Excel was highlighted by the MtGox vs. Dwolla lawsuit. I'm not going to try to pass the judgement on who was to trying to scam who in that case. But spreadsheet's easy mutability makes them perfect tool for perpetuating scams.

This is not to say that you are a scammer. But so many scammers have asked similar questions to yours that now the onus is on you to differentiate yourself from the previous people.

Thank you very much for the clarification.


No, I am not looking for any clients. I was just trying to get a better "sniff test" on who's asking.

In my experience, the reason that you aren't getting any suitable answers is that you don't look like somebody who isn't interested in learning anything new. Microsoft Office could be actually quite helpful, but you would have to learn how to set up proper Microsoft SQL backend for Microsoft Access and utilize the OLAP functionality there. With the clarification above you made clear that you even aren't a wannabe in big data.

I originally thought that you are something akin to a new instance of the German crackpot LvM (https://bitcointalk.org/index.php?action=profile;u=103358) with his "BTC violates GAAP, result a mess." (https://bitcointalk.org/index.php?topic=211835.0) . But then you wrote like somebody who is forced to use Windows because of the organizational constraints, not because you just "don't wanna".

Thanks again.

Edit: Fixed grammar: double negation removed.