For the uninitiated, low-density parity-check (LDPC) code is an error correction code (ECC) that is used to both detect and correct errors on data that is transmitted from one point to another. All ECC types include correction data, so when information is transmitted with errors, the receiver has enough information to fix the errors without having to ask the source for the data again.
This enables transmitted data to maintain a constant speed as is required with digital television signals. What you don’t want is for the image to freeze repeatedly while waiting for correction data to be sent multiple times.
I am sitting in the terminal waiting for my flight home from – yes, you guessed it – China. I am definitely racking up frequent flier miles this year.
This trip ended up centering on resource pooling in the datacenter. Sure, you might hear a lot about disaggregation, but the consensus seems to be: that’s the wrong name (unless you happen to make standalone servers). For anyone else, it’s about a much more flexible infrastructure, simplified platforms, better lifecycle management, and higher efficiency.
Part two of this Write Amplification (WA) series covered how WA works in solid-state drives (SSDs) that use data reduction technology. I mentioned that, with one of these SSDs, the WA can be less than one, which can greatly improve flash memory performance and endurance.
Why is it important to know your SSD write amplification?
Well, it’s not really necessary to know the write amplification of your SSD at any particular point in time, but you do want an SSD with the lowest WA available.
No, you are not about to read some Luddite rant about how smart phones are destroying our society. I love smart phones and most of you do too. It’s remarkable how quickly we have gone from arguing over the definition of a smart phone to not being able to live without them. In fact, the rapid adoption of smart phones has led to the problem I am going to talk about: smart phones can overwhelm dumb wireless networks.
Many of the networks that carry the wireless data to and from our smart phones are built with chips that were designed before Apple announced the first iPhone® in June of 2007.
August was always an exciting time at my childhood home. We were excited that was school was starting in September and mom was relieved that summer was coming to an end. I remember the annual trips to the local department stores to buy school clothes every year. It was always exciting to pick out a new school clothing and a new winter coat. With only a few stores to choose from, many of us wore similar clothes and coats when classes started.
In part one of this Write Amplification (WA) series, I examined how WA works in basic solid-state drives (SSDs). Part two now takes a deeper look at how SSDs that use some form of data reduction technology can see a very big and positive impact on WA.
Data reduction technology can master data entropy
The performance of all SSDs is influenced by the same factors – such as the amount of over provisioning and levels of random vs. sequential writing – with one major exception: entropy.
Every year I diligently get in line for my annual flu (or more technically accurate “seasonal influenza”) shot. I’m not particularly fond of needles, but I have seen what the flu can do and the how many die each year from this seasonal virus.
When you get the flu shot – or, now, the nasal mist – you and I are trusting a lot of people that what you are taking will actually help protect you. According to the CDC (Centers for Disease Control and Prevention), there are 3 three strains, (A, B &C Antigenic) of influenza virus and of those three types, two cause the seasonal epidemics we suffer through each year.
Have you ever seen the old BBC TV show “Connections”? It’s a little old now, but I loved how it followed threads through time, and I marveled at the surprising historical depth of important “inventions.” I think we need to remember that as engineers and technologists. We get caught up in the short-term tactical delivery of technology. We don’t see the sometimes immense ripples in society from our work – even years later.
I got a flurry of emails yesterday, arranging an anniversary get-together in August at the Apple campus.
We all watch the local weather and wonder how forecasters predict (or in some cases mis-predict) the future of weather. While they may not all agree on the forecast, they do agree that the more current and historical data you have, the better your ability to predict what might happen over the next hours, days and weeks.
A term used to describe this growing amount of information is Big Data, and more and more of it leverages Hadoop, a flexible architecture that provides the analysis tools and scalability required to comb through and utilize all available data.
In today’s solid state drives (SSDs), the NAND flash memory must be erased before it can store new data. In other words, data cannot be overwritten directly as it is in a hard disk drive (HDD). Instead, SSDs use a process called garbage collection (GC) to reclaim the space taken by previously stored data. This means that write demands are heavier on SSDs than HDDs when storing the same information.
This is bad because the flash memory in the SSD supports only a limited number of writes before it can no longer be read.