- SSD’s look like a mechanical hard drive and the server operating system uses standard BIOS calls to access.
- SSA’s are a little different and use a PCI Express (PCIe) interface. The operating system must use a unique set of software drivers specific to the SSA device being used.
Monday, March 24, 2014
This is another topic I’ve been reading a lot about lately. Storage tiering uses expensive faster access drives for frequently used data and slower less expensive access drives for older archive type data.
Typical fastest level tiers in a data center will use an optically connected fiber channel disk array, followed by Small Computer System Interface (SCSI) attached drives, followed by Serial Advanced Technology Attachment (SATA) drives followed sometime even by tape drives. Tape drives – I know – but yes they are still used - typically to take content completely offline and store.
Mechanical drives have been historically used for the fastest tier but as prices drop and operating systems include better support , we’re seeing a lot of much faster solid state memory devices (solid-state drives (SSDs) and I/O accelerator cards (sometimes referred to as solid-state accelerators [SSAs]) used for the faster level tiers now.
What’s the difference between a SSD and an SSA? They both basically do the same thing – the only difference is the data interface.
Because SSA’s use drivers that have been tuned specific to the device, they tend to be a little faster. Both SSD and SSA devices can work together on the same server.
Saturday, March 15, 2014
I get this question a lot. It’s not exactly phrased this way though. Typically it’s along the lines of “What’s the wavelength of the WiFi signals in my home or office?”
Good question and a pretty simple calculation! I do realize with a quick Google search you can look the value up but….. that takes the fun out of it J
First, let’s define wavelength. Electromagnetic radiation is sinusoidal in nature and wavelength, represented by the Greek letter lambda (λ), is a distance measurement usually expressed in meters. Wavelength is defined as the distance in meters of one sinusoidal cycle as illustrated in the figure below.
Most WiFi signals run at around 2.4 Giga Hertz (GHz) or 2.4 Billion cycles per second!
Now, in you home or office, you’ve likely got a lot of other wireless devices (microwave, ovens, cordless phones, baby monitors, etc) operating in this same 2.4 GHz frequency range. In the WiFi world, the 2.4 GHz WiFi signal range is divided into 11 channels and channels can be selected when setting up a wireless network to avoid other devices transmitting in the same frequency range.
Ok – back to our question – what’s the wavelength? Here’s how we do the calculation:
12.5 cm is approximately 4.92 inches and...... that's your wavelength.
Monday, March 10, 2014
Let’s take a quick closer look at cloud computing today starting with Infrastructure as a Service (IaaS). IaaS is one of the three main categories of cloud computing services. The other two are Software as a Service (SaaS) and Platform as a Service (PaaS) – we’ll cover the last two in later posts.
So, basically an organization (larger or small) outsources equipment (hardware) that can include servers, routers, switches, storage, backup, etc. The service provider handles all of the maintenance, updating, connectivity, etc and the client pays on a per-use basis. Some of the common IaaS components include:
- Automation of administrative tasks.
- Dynamic scaling.
- Desktop virtualization.
- Policy-based services.
- Internet connectivity.
IaaS is a cost effective option, especially for small companies that do not want to invest directly in hardware and staff to maintain it. That’s why it is sometimes (and perhaps more accurately) referred to as Hardware as a Service (HaaS).
Who are the big IaaS service providers? Today it’s Amazon, Google and Microsoft. Security has always been a concern when it comes to cloud-based processes and there are a number of smaller enterprise level companies involved including Adallom, Alert Logic, FireBlade, FortyCloud, HyTrust, Imperva, JumpCloud, and Porticor.
Wednesday, March 5, 2014
I’m starting to see the term HetNet used in my reading and even had a student ask me for details this morning. That said – I figured it would make a good blog post.
HetNet is short for Heterogeneous Network and is a term currently being used in the wireless world. Most of us are carrying around smartphones with a number of different antennas built in for access via different network technologies. The neat thing about HetNets is they are able to maintain mobile connectivity (no dropped connections) when switching between different wireless connection technologies.
The three different connection technologies getting all the HetNet buzz right now are LTE, Carrier WiFi, and enterprise femtocells. LTE is 4G cellular service and Carrier WiFi is just WiFi service provided by a wireless carrier. Femtocells are small cell devices that are connected to an Internet broadband connection.
So HetNets allow a user device to seamlessly switch from network type to network type– LTE to WiFi to femtocell and vice-versa back and forth without dropping a connection. Pretty neat.
Now, not too long ago, it was believed LTE would be the dominant mobile technology and there would not be a need to alternative type technologies like Carrier WiFi and femotocells. But think about it…… there is only a limited amount of spectrum and bandwidth so providers are looking for ways to lower the number of devices per cell. There are also advantages to having users as close as possible to the different types of base stations.
As a result, we’re seeing providers like Verizon Wireless and AT&T use HetNets to improve the coverage of their network, increase network capacity to match user demand. enhance the user experience, and lower the cost of delivering mobile broadband services.