All Primes Below 10 Million

2012-02-11T18:33:00.000-08:00

Using the Sieve of Eratosthenes, I found all primes below 100 million in one minute and 49 seconds. This is mainly a reference for myself but others may find it useful.

Download primes.txt

The Power of Compounding

2011-12-27T09:03:00.001-08:00

Regardless of your age or situation, time is on your side. Compound interest is the snowballing effect that happens when your dividends and capital gains also generate earnings. Essentially you are making money off of money you already earned in the form of interest.

Let’s say you made a hypothetical investment of $10,000 in a low cost index fund that returned 8% per year on average. If you sold your shares one year from purchase, you would have $10,800. Compounding happens when you keep your shares invested and reinvest any capital gains and dividends you may have earned (in this case $800).

At the beginning of year two, you have $10,800 still faithfully stashed away in your index fund. When you check it again around Christmas time, you notice… an $864 return! Your fund has reached $11,664 ($10,800 reinvested + $864 in interest earned). Notice your interest for year two was large than year one? That’s the power of compounding. Your earnings from a previous year also gain additional interest.

The sooner you start saving, the more significant the effects of compounding can be on your savings. Even if you can only will yourself to save just a dollar a day, the accompanying chart shows how much you could have saved w

AWS Cloud Outage Causes Misunderstanding

2011-12-27T08:54:00.001-08:00

Amazon Web Services (AWS) went down early Thursday morning, placing hundreds of sites offline. Amazon engineers kept the world updated on their progress as they restored service over 30 hours after it went down. Several popular sites like Reddit, Foursquare, and Netflix rely on Amazon’s infrastructure to power all or a portion of their services. Amazon’s downtime presents a perfect opportunity to clarify what may be a grey area when people think about public cloud providers. When people think of Cloud, they think of accessibility, availability, and scalability. Did Amazon Web Services break the core philosophy of cloud? Let’s take a look. The National Institute of Standards and Technology (NIST) provided this definition:

“Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction.”

A traditional hosting model stipulates that you buy a specific resource (like 10 GB of web hosting) for a fixed price ($5.00 per month). Under the traditional model, you pay the full $5.00 even if you only end up using 2 GB of space. Cloud computing offers a variant on this model: pay only for the resources you actually use. The definition above says nothing about availability.

False Sense of Availability

Amazon has baked redundancy into many of their products including Amazon S3 and Amazon SDB. They even advertise a reduced redundancy option for S3 (which is still redundant but less so) and you pay less for it. Now, if Amazon S3 went down for an entire day, that doesn’t mean it wasn’t redundant. Your data is still safe against hardware corruption and failures. It means the service was unavailable. I’ll be the first to admit I sort of merged the two features together in my mind when I first looked into using Amazon’s cloud. I thought cloud meant availability at all times. But if you take a look at their site, they state that EC2 is guaranteed to be available 99.95% of the time. Amazon did not violate their service level agreement (SLA) when this outage occurred.

Cloud Does Not Promise Availability Unless You Pay

At the end of the day, a piece of commodity hardware with a virtualization layer is plugged into the same physical world every other hosting provider has to abide by. Cloud is just as susceptible to natural disasters and storms like any traditional provider. Any Amazon customer who experienced an outage could have chosen to mirror their configuration in other availability zones. Their risk analysis probably concluded that the cost of a single availability zone improved their bottom line more than a short outage would hurt it. Amazon offers the capability to replicate servers across many regions, but you have to be willing to pay for it. The same is true in a traditional data center. Redundancy and availability cost money. I think availability is a service level agreement (SLA) issue and is different from the definition of what Cloud stands for. Cloud is a paradigm that describes how we consume resources (compute, storage, or services) on demand. That idea says nothing about the guaranteed service level it provides (other than the nearly instantaneous elasticity of resources) otherwise everyone would be operating under a universal SLA to satisfy the definition of what a cloud should be. What are your thoughts?

Adam Fisher

All Primes Below 10 Million

The Power of Compounding

AWS Cloud Outage Causes Misunderstanding

False Sense of Availability

Cloud Does Not Promise Availability Unless You Pay