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Ray Ozzie to leave Microsoft

2010-10-18T23:38:00Z

Ray Ozzie, Microsoft's chief software architect and the executive responsible for pushing the company into the cloud, plans to step down, Microsoft said on Monday.

Quase 70% da classe C brasileira já têm acesso à Internet, diz pesquisa

2010-10-25T19:56:38Z

Desktops conectados à Web estão em 40% dos lares desta classe, seguidos pelos celulares e laptops. Número de internautas cresceu 44% em seis anos.

GVT reduz preços da banda larga

2010-10-26T13:55:46Z

Novo portfólio, anunciado na 12ª edição da Futurecom, inclui plano de 15Mbps, a R$79,90.

Can Oracle Turn Java Around?

2010-10-25T08:00:00Z

A lot has happened in the last week or two in the Java space. Oracle has remained silent throughout, but their silence is deafening. They need to clarify what is happening with the JCP, and comment on OSX's removal of Java. Oracle can still turn this around, but the silence is damning. They may have bought the rights to Java, but it hasn't bought into the Java community. By Alex Blewitt

The Zombie Network: Beware 'Free Public WiFi' (Travis Larchuk/NPR)

2010-10-11T08:20:00Z

Travis Larchuk / NPR:
The Zombie Network: Beware ‘Free Public WiFi’ … It's in your airports, your coffee shops and your libraries: “Free Public WiFi.” — Despite its enticing name, the network, available in thousands of locations across the United States, does not actually provide access to the Internet.

The Future of Java: forking, death, or stasis?

2010-10-06T16:28:39Z

Is it time to consider replacing Java? Java pundit and former Editor-in-Chief of TheServerSide.com, Joseph Ottinger, steps into the fray by proposing some options, alternatives, and more to the point, a reality check.

Especial Carreira: TI paga 30% mais no Sudeste

2010-10-07T12:15:00Z

Executivo, na região, é demandado por atitudes mais estratégicas e precisa ter maior domínio de línguas

Concurso do Banco Mundial dá US$ 45 mil a desenvolvedores

2010-10-11T15:02:00Z

Projetos devem estar ligados a uma das oito Metas de Desenvolvimento para o Milênio (MDGs)

Selling Scrum to Your Manager?

2010-10-07T06:00:00Z

Trying to Sell Scrum to Management? Failing and wondering why? This often happens in the days after someone returns from a CSM course ready to help change the world. By Mark Levison

Article:LinkedIn Signal: A Case Study for Scala, JRuby and Voldemort

2010-10-11T08:48:00Z

On September 29th LinkedIn Signal was announced, providing a social search application both for LinkedIn shares and tweets from LinkedIn-Twitter bounded accounts. This article aims to provide more insight into the motivation and technical challenges of combining Scala, JRuby and Voldemort, at such scale. By Dionysios G. Synodinos

Moving from Spring to Java EE 6: The Age of Frameworks is Over

2010-10-04T15:42:30Z

Frameworks solved the J2EE problem. But with Java EE 6, it's time to put away the biases that your frustration with J2EE created. Frameworks are a thing of the past. Java EE 6 extensions are the future.

Java - Programming - Languages - Spring Framework - Enterprise Edition

Redes sociais: 13% das empresas bloqueiam acesso

2010-09-30T19:29:00Z

Segundo pesquisa, 81% restringem o uso de pelo menos uma ferramenta da Web 2.0 em função de preocupações com a segurança

More on dangers of the caches

2010-09-24T00:18:58Z

I wrote couple of weeks ago on dangers of bad cache design. Today I’ve been troubleshooting the production down case which had fair amount of issues related to how cache was used.

The deal was as following. The update to the codebase was performed and it caused performance issues, so it was rolled back but yet the problem remained. This is a very common case when you would see customer telling you everything is the same as it was yesterday… but it does not work today.

When I hear these words I like to tell people computers are state machines and they work in predictable way. If it does not work same today as it worked yesterday something was changed… it is just you may not recognize WHAT was changed. It may be something subtle as change in query plan or increase in search engine bot activity. It may be RAID writeback cache disabled due to battery learning but there must be something. This is actually where Trending often comes handy – graphs would often expose which metrics became different, they just need to be detailed enough.

So back to this case… MySQL was getting overloaded with thousands of same queries… which corresponded to cache miss storm but why it was not problem before ? The answer lies in caching as well. When software is deployed the memcache is cleared to avoid potential issues with different cache content, so system have to start with cold cache which overloads the system and it never recovers. When you have expiration based cache you increase the chance of conditions when system will not gradually recover by populating cache – if because of cache misses performance is so bad the speed of populating cache with new items is lower than speed with which items expire due to timeout you may never get a system warmed up.

But wait again… was this the first change ? Was not the code ever updated before ? Of course it was. As often with serious failures there is more than one reason which pushes system over top. During normal deployment the code change is done at night when when the traffic is low, so even if system has higher load and worse response time for several minutes after code is updated, the traffic is not high enough to push it to conditions it is unable to recover. This time code update was not successful and by the time rollback was completed the traffic was already high enough to cause the problems.

So the immediate solution to bring the system up was surprisingly simple. We just had to get traffic on the system in stages allowing Memcache to be warmed up. There were no code which would allow to do it on application side so we did it on MySQL side instead. “SET GLOBAL max_connections=20” to limit number of connections to MySQL and so let application to err when it tries to put too much load on MySQL as MySQL load stabilizes increasing number of connections higher until you finally can serve all traffic without problems.

So what we can learn from this, besides cache design related issues I mentioned in the previous post.

Include Rollback in Maintainance Window Ensure you plan the maintainance window long enough so you can do rollback inside this window and do not hesitate to do this rollback
if you’re running out of time. Know how long rollback takes and have it well prepared. Way to often I see people trying to make things work until time allocated for the operation is up and when
rollback have to be done outside of the time window allowed.

Know your Cold Cache Performance and Behavior Know how your application behaves with cold cache. Does it recovers or does it just dies with the high traffic ? How high is the response time penalty and how long it takes to reach normal performance ?

Have a way to increase traffic gradually There are many reasons beyond caching when you may want to slowly ramp up the traffic on the system. Make sure you have some means to do that. I’d recommend doing it on user session so some users are in and can use the system completely while others have to wait for their turn to get in. It is a lot better than having it done on page basics when you randomly have some pages giving error messages. In some cases you can also do ramp up feature by feature.

Consider Pre-Priming Caches In some cases when cold performance gives too bad response time you may want to prime the caches by running/replaying some production workload on the system before it is put online. In this case all ramp up and suffering from bad response time can be done by script… which does not care.

Entry posted by peter | 5 comments

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50 Open Source Tools That Replace Popular Education Apps

2010-10-03T04:10:53Z

Open source educational software is rapidly gaining adoption in a wide array of teaching environments.

CPM Braxis tem 173 oportunidades em TI

2010-09-30T14:09:00Z

São 108 vagas para estudantes universitários e 75 para profissionais técnicos

Gosling Unleashes on .NET, IBM, Glen Beck, iPads, Oracle & Others

2010-09-23T00:54:32Z

"They'd do anything they can to screw Sun over. I mean, they didn’t name Eclipse casually." That's just one of the many gems James Gosling floats in his interview with the folks at BasementCoders.com

Oracle Corporation - IBM - Sun Microsystems - James Gosling - Oracle

10 motivos de fracasso do outsourcing

2010-09-20T11:05:00Z

Confira lista elaborada pela consultoria everis

iPhone 4 chega às lojas brasileiras na sexta-feira

2010-09-15T12:26:12Z

O iPhone 4, próxima geração de smartphones da Apple, chega ao Brasil na próxima sexta-feira (17), segundo informações confirmadas à Folha pela assessoria de imprensa da TIM nesta terça-feira (14).

Yonhap -18.ago.07/Efe

TIM confirmou que iPhone 4 (foto) chega ao Brasil na madrugada de sexta-feira; empresa não diz preços

Algumas lojas da operadora estarão abertas para aquisição do aparelho às 00h da próxima sexta. Leia mais (14/09/2010 - 19h37)

Twitter anuncia novo layout

2010-09-15T12:26:08Z

A rede social da internet Twitter anunciou nesta terça-feira uma remodelação de sua plataforma de mensagens curtas a fim de criar uma 'experiência mais fácil, rápida e rica' para os usuários, segundo a empresa. O novo layout é dividido em duas partes: na esquerda permanecem as listas de tuítes como o modelo antigo, porém, na parte esquerda o usuário poderá ter acesso a vídeos e fotos postadas sem sair da páginas -- basta clicar sobre a mensagem. Atualmente, para ver links anexados é preciso abrir uma nova janela. Leia mais (15/09/2010 - 03h02)

Revisiting Solid State Hard Drives

2010-09-15T09:30:23Z

It's been almost a year since I covered The State of Solid State Hard Drives. Not a heck of a lot has changed, but the topic is still worth revisiting, because if you care at all about how your computer performs, solid state hard drives remain a life changing experience. Here's why:

A solid state hard drive is easily the best and most obvious performance upgrade you can make on any computer for a given amount of money. Unless your computer is absolute crap to start with.
The practical minimum solid state hard drive size, 128 GB, has modestly declined in price -- from about $350 to about $250.

(yes, you can get by with 64 GB, but at least with my Windows installs I find that I have to think about disk space with 64 GB, whereas with 128 GB I don't have to worry -- ever. Don't make me think, man!)

The rest of the components inside your PC are downright boring in comparison. CPUs? All stupid fast at any price, with more cores and gigahertz than you'll ever need unless you're one of those freaks who does nothing but raytracing and video transcoding all day long. Memory? Dirt cheap, and average users won't need more than 2 gigabytes of the stuff in practical use, which at the current going rate for DDR3 is less than 50 bucks.

Thanks to the neverending march of Moore's Law, PCs are becoming speedy at any price these days. It's difficult for me to muster any enthusiasm for the latest Intel CPU updates when I spend almost zero real world time waiting for the CPU to do anything on my computer. I guess it's true: absolute power corrupts absolutely.

But hard drives, now, there's where you can pay a bit more and see a groundbreaking, generational leap in performance worthy of that investment -- as long as you skip over the old and busted spinning rust hard drives, and choose a newfangled solid state hard drive.

The current king of the hill seems to be the Crucial RealSSD C300.

Pretty sexy, right? Oh, who am I kidding, it's a boring slab of aluminum and silicon. But like all truly sexy things, what turns me on is the part I can't see -- the sexy, sexy, sexy performance inside this baby.

See those bars dragging down the bottom of this graph? All spinning rust. Heck, even the SSD I recommended last year is only middle of the pack here. AnandTech concurs -- the Crucial RealSSD C300 is top dog, at least for now.

(Be careful, though, that your operating system supports the SSD TRIM command, otherwise you'll suffer severe performance degradation over time with almost any SSD. Operating systems earlier than Windows 7 and the latest, greatest Linux kernel should beware -- and, shockingly, OSX still doesn't support TRIM!)

Where it gets trickier, though, is when you need more than 128 GB of storage, or when you are limited to one 2.5" hard drive -- like in a laptop. In that case, ideally you'd like something that has the speed of a solid state hard drive, but the capacity (and economical price per gigabyte) of a traditional magnetic platter hard drive. You might say … a hybrid hard drive, the kind I was dreaming about back in 2006 …

After all this analysis, it's clear to me that traditional hard drives and flash memory are quite complimentary; they're strong in different areas. But flash drives are the future. They will definitely replace hard drives in almost all low end and low power devices-- and future high performance hard drives will need to have a substantial chunk of flash memory on board to stay competitive.

I had always been disappointed that hybrid hard drives, drives that combine both flash memory and traditional magnetic platters, never came to fruition. It was either traditional or SSD and nothing in between. It seemed like such an obvious "best of both worlds" scenario to me. But I recently discovered that decent hybrid drives do finally exist -- though in a small and mostly unheralded way.

Seagate's Momentus XT takes a totally respectable 2.5", 7200 RPM drive with a 32 megabyte buffer and combines it with 4 gigabytes of flash memory. The result is the exactly what I had always hoped:

Seagate's Momentus XT should become the standard hard drive in any notebook shipped. The biggest problem I have with using any brand new machine, regardless of how fast it is, is that it never feels fast because it usually has a HDD and not an SSD. While the Momentus XT isn't quite as fast as an SSD, it's a significant improvement over the mechanical drives found in notebooks today.
In many cases the Momentus XT performs like a VelociRaptor, but in a lower power, quieter package. The impact of adding just a small amount of SLC NAND is tremendous. The potential for hybrid drives continues to be huge; what Seagate has shown here is that with a minimal amount of NAND you can achieve some tremendous performance gains.

And the best part? 500 gigabytes of near-SSD performance for $130! Or, if that's too spendy, how about 320 gigabytes of near-SSD performance for $99?

I've ordered a few of these drives to upgrade my laptops and home theater PC. Sure, I'll invest in a SSD for my beastly desktop, but I can't justify $300 to put a SSD in a laptop I spent all of $800 on, or a home theater PC that set me back a mere $500. But a hundred bucks for near-SSD performance and decent capacity? Sign me up. And hard drive vendors: although I love SSDs to death, please keep these improved hybrid drives coming, too, please!

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