Shoeshining


In tape backup, shoeshining (also known as backhitching) is the repeated back and forth motion a tape drive makes when there is interruption in the data stream.
When data is sent to tape, it needs to flow at the same speed the tape is running. If there is a mismatch between speeds, the tape drive will try to accommodate it. For instance, if abackup server is sending data slower than the tape drive processor writes it, the drive will periodically stop and wait for data to catch up. Once the drive determines there is enough data to start writing again, it will rewind to the exact place where the last write took place, reset the tape heads and continue. All this happens very quickly; to the casual observer, the wheels on the tape drive just seem to stop and jerk back and forth (like someone shining their shoes) before moving forward smoothly again.
Because tape is a medium that requires blocks of information to be recorded or read sequentially, blank spaces are not acceptable. Buffers (temporary storage areas) can help with temporary speed mismatches, but they can fill up or empty when the mismatch is chronic.
Excessive shoeshining indicates there is a problem. Repeated back and forth motion not only causes a degradation of service, it also causes excessive wear and tear on both the tape and the tape drive. To prevent shoe-shining, backup administrators need to strike the right balance between the number and speed of backup tape drives, the amount of data being sent to the tape library and the connectivity between components.

Stateless App


A stateless app is an application program that does not record data generated in one session - such as information about user settings and events that occurred -- for use in the next session with that user. The trend toward cloud computing is driving interest in stateless apps.


In a computing context, "state" can be defined as a set of conditions that exist at a given point in time. A stateful application records information about changes in state caused by events during a session, including those caused by user interaction. That means that the application can call up information that will enable configuration changes and so on to remain consistent from one session to the next. The need to retrieve state information, which may be stored on the client device or a remote server, can increase the demand for bandwidth.


Web apps are usually stateful, as are most of the APIs (application-program interfaces) that interconnect them with other Web apps and services. In a cloud environment, however, it's preferable that apps be stateless for the sake of scalability and portability. Furthermore, many important cloud technologies are not equipped to deal with state data. Amazon, for example, recently announced that it was implementing what it called sticky sessions - a mechanism for passing on state data - because its elastic load balancing (ELB) implementation was found to break stateful apps.

Metro Apps

Metro apps are touch-screen-friendlyapps written especially for Microsoft'sSurface line of tablet computers.
Metro apps are available from the Windows store for use on any computer that runs Windows RT or Windows 8. The apps will work not only on tablet devices, but also on any desktop or notebook computer that uses a keyboard and mouse, provided that the correct OS(operating system) is installed. Microsoft plans to introduce Metro apps to support communications, scheduling, news, weather, sports, financial information, music, videos, books, travel, and other popular consumer activities. In addition, there will be an app for cloud storage.
The original designers of Metro apps based their approach on a perceived consumer demand for apps that are engaging, immersive, interactive, touch-based, and usable in multiple form factors. They are built for a tiled UI (user interface) with limited, intuitive, functional graphics. Metro apps are based on the Metro design language, originally conceived for mobile Internet devices (MID) and smartphones.

Sideloading

Sideloading is the installation of an application on a mobile device without using the device's official application-distribution method.

Sideloading works differently on different mobile platforms. To enable sideloading on an Android OS device, for example, the end user simply checks a box in the operating system settings. On an Apple iOS device, however, the end user must jailbreakthe device to enable sideloading. Once sideloading is enabled, the user can download and install applications from any website or third-party app store.

Sideloading offers mobile device users a way to access more applications than are available through commercial app stores such as Google Play or the Apple App Store, but it is important for the end user to understand there can be risks. Commercial app stores screen for malware and other threats and assume responsibility for digital rights management (DRM). Applications from other sources may not have been screened for malware and may be pirated.

Software-defined networking (SDN)

Software-defined networking (SDN) is an approach to networking in whichcontrol is decoupled from hardware and given to a software application.

When a packet arrives at a switch in a conventional network, rules built into the switch's proprietary firmware tell the switch where to forward the packet. The switch treats sends each packet going to the same destination along the same path, and each packet is treated the exact same way.

In an SDN, however, the network administrator uses third-party software to shape trafficfrom a centralized control console. The administrator can change the switch's rules when necessary -- prioritizing, de-prioritizing or even blocking specific types of packets with a very granular level of control. This is especially helpful in a cloud computing multi-tenantarchitecture because it allows the administrator to manage traffic loads in a flexible and more efficient manner.

SDN is sometimes referred to as the "Cisco killer" because it allows network engineers to support a switching fabric across multi-vendor hardware and application-specific integrated circuits (ASICs). Currently, the most popular specification for creating an SDN is an openstandard called OpenFlow.

Cloud Database




A cloud database is a database that has been optimized or built for a virtualized computing environment.


Optimizing an already existing database for the cloud provides benefits such as:


The ability to pay for storage capacity and bandwidth on a per-use model.
The ability to move the database from one location to another (cloud portability).
Scalability on demand.
High availability (HA).
Putting the database in the cloud can be an effective way to support and cloud-enable business applications as part of a wider software-as-a-service (SaaS) deployment by simplifying the processes required to make information available through Web-based connections.


Another benefit of moving a company's databases to the cloud is storage consolidation. Databases in multiple departments of a large company, for example, can be combined in the cloud into a single hosted (DBMS).

Electrical pollution


Electrical pollution is electromagnetic-field (or EM-field) energy emanating from electrical wiring. In most places, the majority of this energy exists at 60 Hz (hertz), resulting from the AC (alternating current) that constantly flows in the utility wiring outdoors, indoors, and inside common appliances.


Not all of the energy in utility electricity occurs at the standard AC frequency of 60 Hz (50 Hz in some locations). Emissions also take place at various other frequencies. These emissions, sometimes called dirty electricity, result from the use of appliances that generate irregular waveforms and transmit the resulting currents into the utility wiring. Vacuum cleaners, hair dryers, fluorescent lamps, and some consumer electronic devices produce this type of energy.


In recent years, controversy has arisen concerning alleged adverse health effects from electrical pollution. Some scientists believe that electrical pollution has been a major cause of human ailments ever since the very first use of AC utility electricity (around the year 1900). Others deny that any conclusive evidence exists for adverse health effects in humans.