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bitminer commented on Metastable Failures in Distributed Systems [pdf]   sigops.org/s/conferences/... · Posted by u/zekrioca
mjb · 4 years ago
I think this paper is super important, and anybody who designs or runs big systems should read it and take the core point to heart. As system designers, we're very used to thinking about systems as 'stable' and 'unstable', where stability is good, and instability is bad. What this paper points out is that many kinds of distributed systems have multiple 'stable' modes, some of which are modes where the system is stable (in a control theory sense), but not doing any useful work from the client's perspective. This is dangerous, because the system won't kick itself out of this "stable but down" mode without something changing: human input, a control plane taking action, etc.

I don't think this paper covers anything particularly new, but writing it down in this form, with the evidence they present, is very valuable. Hopefully this paper will deepen the conversation about applying control theory to distributed systems design and control problems, and allow a more theoretical approach to be taken to the design of these systems to avoid common causes of instability and bistability.

One of the authors has a great summary of the paper on his blog: http://charap.co/metastable-failures-in-distributed-systems/

I wrote a summary and discussion too: https://brooker.co.za/blog/2021/05/24/metastable.html

bitminer · 4 years ago
It is a useful paper, yes. Good examples, good diagnosis of issues in systems theory, good definition of a way forward.

However it suffers from (a) weak definitions and (b) implausible or strange descriptions.

For (a), what is a "strong feedback loop"? Does it have high gain (low error) or high bandwidth (fast)? Is it hidden (the accidental link imbalance example)? Is it obvious (the cold cache example)? What makes it "strong"?

Or, conversely, what is a "weak" feedback loop?

A number of acronyms are undefined (SRE, LIFO). I think I know what they mean, and most HN readers will too. What about the other readers?

And using Wikipedia to define metastability? There must be a more persistent or academically defendable reference. Wikipedia is OK for informal definitions. In a paper calling for more academic studies this is ironic.

(b) Section 2.1 "When replicas are sharded differently..." Huh?

Section 4 "upper bound" used as a verb. Should be "limit or place bounds on".

Section 4 "The strength of the loop depends on a host of constant factors from the environment..." Odd, the term is not defined but this is the second dependency listed. Very strange.

In short it needs/needed a better reviewer.

That all said, it has summarized a lot of good ideas on controlling stability in distributed systems.

Other references may be found in Adrian Colyer's "the morning paper". No longer updated but has many years of good references. See blog.acolyer.org.

bitminer commented on Launch HN: BlackOakTV (YC S21) – Netflix for black people    · Posted by u/Uzo0312
kadabra9 · 4 years ago
Just from an addressable market standpoint, it seems like you have work cut out for you given that you’ve essentially isolated your product to 13-14% or so of the US population. Not to mention those in that segment that already sub to Netflix , other streaming services etc.
bitminer · 4 years ago
Especially since Netflix has a lot of entertainment featuring black actors, producers etc. from the US. And a lot of Nigerian and South African productions too.

You just have to look for it.

bitminer commented on Backblaze Drive Stats for Q2 2021   backblaze.com/blog/backbl... · Posted by u/LaSombra
ksec · 4 years ago
CDs and DVD degrade over time, I think this is primarily those with home recording CD / DVD-Rs. I am not sure what the difference is with Factory made CDs or DVDs like Music CD or DVD from Playstation 2 but those seems to be fine. I think I need to look this up that you have brought it to my attention.

But do HDD last longer if they are unplugged. And only start up when they are needed? In that case wouldn't an NAS putting HDD to sleep most of the time would prolong the life time of HDD?

bitminer · 4 years ago
Be very aware -- SSD must be plugged in otherwise they may lose data after a few years.

The time varies with temperature. Search for SSD data retention for more info.

The JEDEC standard is the one to read.

bitminer commented on Digital-only artwork fetches nearly $70M at Christie's   reuters.com/article/idUSL... · Posted by u/afkqs
KaiserPro · 5 years ago
not to mention that the art its self is cheap, derivative and with no inherent meaning, unless you count the act of getting $70m for not actually selling the work as actual art.
bitminer · 5 years ago
21.7 cents per pixel.

Stock photos cost $5 to $100 and come with distribution rights.

Somebody paid a lot of money for bragging rights.

bitminer commented on Launch HN: Albedo (YC W21) – Highest resolution satellite imagery    · Posted by u/topherhaddad
slingnow · 5 years ago
I don't see your e-mail address anywhere. I'm interested in such a product.
bitminer · 5 years ago
Non rapid updates to HN profile, I guess.

hncollector@ and the domain is bitminer.ca

bitminer commented on Launch HN: Albedo (YC W21) – Highest resolution satellite imagery    · Posted by u/topherhaddad
bitminer · 5 years ago
I have a demo website that is "4-clicks" to ordering satellite imagery. Include one for the data type, and one for the date.

Contact me by email if you would like a demo. (I'm trying to avoid HN overload.)

bitminer commented on DECO – Using cell phones to detect cosmic rays and other energetic particles   wipac.wisc.edu/deco/data... · Posted by u/agmm
bitminer · 5 years ago
There is also the CREDO app, check the Google Android app store.
bitminer commented on Sealed U.S. Court Records Exposed in SolarWinds Breach   krebsonsecurity.com/2021/... · Posted by u/picture
skoskie · 5 years ago
Hey devs! The article indicates jetbrains software might be compromised.
bitminer · 5 years ago
And the New York Times article might be true.

I'm sure that Solarwinds uses many more developer tools than what Jetbrains supplies. But only Jetbrains was "founded by Russians" so the NYT leads with that.

u/bitminer

KarmaCake day117November 21, 2017View Original