Has Amazon EC2 become over subscribed? (2010)
alan.blog-city.com
alan.blog-city.com
One of the key contributing factors to this kind of network degradation of AWS (/or other cloud vendor) is the abundance of the "bad neighbor test" - where a client performs tests to see if they can achieve a 'preferred' amount of CPU/IO on the host of their new instance.
Resource sharing rules at the host level actually means that if everyone is trying to max out their instance, you would still get the equal share you are entitled to and guaranteed with your instance, so what the bad neighbor test really means is whether you can actually go into your neighbor's CPU allocation due to their under-use.
Well, if everyone does that then the system degrades as someone has to a party using less than their allocation and the amount of instance spots that don't fail the 'bad neighbor test' become non existant.
The overall health of the entire network would actually be better if folks didn't do this practice and instead everyone simply evened out their use across their instances that enjoy additional resources and stuck it out with the %age of their instances that only achieved their guaranteed minimum resource use and no more.
My company uses another "cloud-like" vendor and although we don't perform 'bad neighbor' tests upon new instances, it is fair to say our application benefits from the fact that the majority of the instances on their network are under-utilized and we can push into the max CPU of the host beyond the limits we pay for. Where instances do share 'bad neighbors' (ie we can only get what we paid for and no more - boo hoo, etc) we still keep the instance but simply route around that and distribute less load than on other nodes in our network.
That doesn't become the most cost effective mechanism, but the "savings" of the 'bad neighbor test' are probably negligible and ironically by not doing this we become the "good neighbors".
That's the part that doesn't scale.
Makes sense from Amazon's perspective, of course - less promises to keep, more flexibility.
Can't blame people for measuring the performance empirically, in the absence of hard guarantees. Just that produces results that happen to be wrong.
Other than the "I/O Performance", I think all of their specs are pretty well defined if you're willing to dig up the appropriate docs.
To be fair it's understandable why Amazon doesn't promise these features will or won't be present - it would make their already-complicated product offering even more complicated. And for a great many applications, customers won't be sensitive to details like CPU cache and disk performance.
But on EC2 Dedicate Instance (ie single tenancy) my guess is that if your application (or, business model) relies on each of your nodes being able to utilize more than your equal share on the host then in fact you would NOT want more than one of your instances to exist on the same physical host, in order to maximize the chances that each instance can grab all of the resources on it's given host.
If this is your model, having all your instances on the same physical host would be disastrous. In fact, there's (economic) argument for Amazon offering customers the complete opposite - pay to guarantee that no two instances are ever instantiated on the same physical host.
Then I saw:
Published: 9:01 AM GMT, Tuesday, 12 January 2010
That said, what is the deal with the internal network latency and the other points the OP touched upon today? Did Amazon get around to resolving things, or have things worsened?
The flexibility of usage-based billing and instant provisioning is awesome, but it's really not worth giving up dedicated performance IMHO.
The big costs you pay for on AWS are the engineering, networking and UI development. Dedicated servers should be easier to provision and manage and he probably has a much smaller team.
So theoretically, it is possible that his prices are half as much as Amazon and he still makes a decent profit.
http://blog.carlmercier.com/2012/01/05/ec2-is-basically-one-...
Compare youself: https://www.ovh.com/us/dedicated-servers/
Thank you...so much for posting this.
The largest instances (the quad- and octuple-extra-large) likely are on their own servers but I've never seen that explicitly confirmed anywhere.
> Dedicated Instances are Amazon EC2 instances launched within your Amazon Virtual Private Cloud (Amazon VPC) that run hardware dedicated to a single customer.
"An additional fee is charged once per hour in which at least one Dedicated Instance of any type is running in a Region."
So it's not like they are charging $10/hr/instance (so it amortizes over all of the dedicated instances)
c1.xlarges still underperform far under what I'd expect.
Is it possible to run any cloud service at Amazon's scale without these issues?
(genuine questions speaking from a point of ignorance)
SANs in a cloud environment optimize for the wrong thing. Servers by and large have a high uptime -- since their falling over is comparatively rare, this is simply a problem I've never had difficulty with. What I have had in spades, before I learned better, were database problems due to wild fluctuations in latency to the SAN.
It doesn't help that when SANs kick the bucket, they tend to affect a lot of things.
Rather than "strictly local storage", I'd say "keep storage as local as possible", but there are absolutely times where keeping it in-chassis isn't optimal.
(I wonder if British law considers a corporation to be a person to the degree that US law does, or if this plural view of a corporation is pervasive in law as well as in grammar.)
Edit: For example, here's what the Guardian's style guide says on the matter:
http://www.guardian.co.uk/styleguide/c#id-3022716
Of course, with something as flexible and constantly evolving (and as used and abused) as the English language, it is usually possible to find examples and counter-examples for just about anything. There are also edge cases; the Guardian refers to police forces as plural entities, I believe. Suffice to say, when I was running a back bench, singular was the order of the day when it came to company names.
But then I never won any awards for grammar.
But for me, when speaking and writing consider companies to be groups of people, and so I use plural. And I think that is common over here in Britain.
That should be explanation enough.
I'm intrigued that you are ready to rule out the contributions of a class of people who manipulate the written word for a living (and debate usage among themselves to the point of distraction!)
ASDA? Well, I'd use "Asda" since it is pronounced as a word, not four initials. But the company itself still seems to be struggling for consistency on that...
I'm not a linguist but parsing these sentences as an American reader, I feel a bit like this page's examples are playing games with word order and omission. The cited "prestige" grammar sounds less intuitive to me not because of the pronoun used, but because of word order and words that are left out.
Example cited as correct prestige grammar:
> They didn't give anyone that worked less than she a raise.
That sounds a little weird to my American ears, but "worked less than she did" sounds totally correct.
"Worked less than her" (cited as correct non-prestige) sounds a bit casual and informal, not sounding too jarring but not what I'd expect in decent writing. Similar to the other example of "us commuters". If I'm talking to someone I wouldn't blink if they said this, but I wouldn't see it in the New York Times. (Though this also reminds me of phrases like "me too" or "it's me", which despite being inconsistent with distinctions between subject and object in other phrases, you'd hear a lot more than "I as well" or "it is I".)
> Mary and him are late.
Sounds very wrong to me.
Thinking back to my childhood it was pretty common for kids to be a bit "confused" about using pronouns this way before 10 years old or so, so maybe there is something to the author's statement that kids learn the non-prestige form and then the educated ones are "corrected" later.
> Mary and he are late.
This still sounds weird. I'd say "he and Mary are late".
> her and us
> she and we
These sound pretty clumsy regardless of which is supposed to be used.
An English person, writing English in an English way, and you say you're not going to continue reading. Do you require him to write like an American? Why should an English person, writing their own language, have to follow your conventions?
"I didn't know"
Well then don't start shouting your mouth off! If you don't know, keep quiet.