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Comment by uvdn7 | Hacker News Reader

For the fun issues you described, read-modify-write (either using optimistic concurrency control or pessimistic) can work, if I understand your question correctly.

Spanner is awesome and one of my favorite systems/papers. I think it would be very computational and power expensive to run the social graph workload on a spanner-like system. Do you have an estimate of how many megawatts (if not more) are needed to support one quadrillion queries a day on Spanner?

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I wish I had more solid data. Cloud Spanner claims about 10K read QPS and 2K write on a "node" which costs $1/hour. The Spanner paper reports about 10K read QPS per core. As I understand the cloud deployment it's 3 replicas at that price, so $0.33/hour should buy me about 8 cores and so I'm not sure what the disparity is (maybe markup? CloudSQL is 2X the cost of compute), but I'll go with 10K QPS/8 cores at the low end. Anyway, something like 500-1000W for ~100 cores so something between 100 QPS/W and 10 QPS/W using the 1000W and high and low performance estimates, or 10^15 / 86400 = 11.6e12 QPS for somewhere between 116MW and a a little over a GW. Sounds comparable(?) to MySQL+TAO on the low end to ridiculously expensive at the high end.

EDIT: I have no clue how efficient MySQL+TAO really are but figure that at least tens of thousands of machines go into it.

It that's on x86_64 than the power budget seems some ten times too low for me. A typical Xeon Silver 4208 is 10 W TDP per core, and other things would also add up, even taking into account that newer CPUs are more efficient.

I am basing this off of Epyc Milan which looks closer to 5W/core, and possibly mutilating my language a bit because I think cloud products are sold by thread (vCPU), not by physical core.

I was actually a little surprised how hard it is to get performance/W figures since I don't currently have any physical server hardware to go off of.

I can't give away details/numbers. But I have to say, what you did right here is very impressive.

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