# Category Archives: Tech

## Hard Drive Capacity And Performance

A hard disk is one of the main storage media for a computer, It’s consisting of one or more aluminum or glass discs. The magnetic material is covered outside the disc.

Hard disk has a solid state disk (SSD disk, new hard disk), mechanical hard disk (HDD traditional hard disk), mixed hard disk (a new hard disk based on traditional mechanical hard disk). SSD uses flash memory particles to store, HDD uses magnetic disk to store, mixed hard disk (HHD: Hybrid Disk) is a hard disk that integrates magnetic hard disk and flash memory. The vast majority of hard drives are fixed drives that are permanently sealed and fixed in a hard disk drive.

When you buy the hard disk, you probably will find that the actual capacity of the hard disk will be smaller than the parameters marked, such as the purchase of 3TB hard disk, click on the computer properties to view the capacity of hard drive, that capacity is only 2.72TB, the differences are 0.28TB, which is equal to more than half of the 500GB hard disk. Will you feel being cheated?

However, When it comes to the capacity conversion of a hard disk, Manufacturers choose the decimal system while computer use binary system. The conversion between them needed.

Here’s the different capacity calculation formula:

Hard disk vendor decimal calculation:

3000GB = 3000,000MB = 3000,000,000KB = 3000,000,000,000Byte

Operating system binary calculation:

3000GB = 3072,000MB = 3,145,728,000KB = 3,221,225,472,000Byte

1GB of the actual byte (Byte) calculation:

1GB = 1024MB * 1024KB * 1024Byte = 1,073,741,824Byte

The actual capacity of 3000GB:

3000,000,000,000Byte / (1024MB * 1024KB * 1024Byte) = 2793.97GB

Why the actual capacity of a 3TB hard drive is 2794.39GB? when manufacturers are producing the hard drive, the disk will be left 0.1-1GB capacity, so the actual capacity is slightly larger than the 2793.97GB.

So in the conversion of 2794.39GB into TB, So in the conversion of TB into the 2794.39GB, after deducting the area occupied by 177MB, the remaining capacity divided by 1024GB, the actual capacity is equal to 2.72TB after rounding, which is the origin capacity of 2.72TB.

So what are the main performance of a Hard drive?

1. Capacity

The capacity of the hard disk is one of the most important technical indicators to measure a hard disk. The capacity of the hard disk is determined by the number of disks (the number of heads), the number of cylinders and the number of sectors, and the formula is as follows: the capacity of the hard disk = the number of disks X the number of the cylinder X the number of the sector X 512B. There are often a number of stacked disk inside the hard disk, therefore, the hard disk capacity can also be calculated: hard disk capacity = disk capacity x disk number.

2. Rotation Speed

Hard disk speed (Rotation Speed) has a direct impact on the data rate of the hard disk, the speed is one of the decisive factors in the transmission rate of the hard disk, but also an important symbol to distinguish the hard disk. In theory, the faster the better, because the higher speed can reduce the average search time and the actual hard disk read / write time, which can improve the read / write speed on the hard disk. But everything has two sides, while the speed increases, the heat of the hard disk will increase, its stability will be reduced to a certain extent. Today the mainstream hard disk speed is 5400rpm (Rev / min), 7200rpm and 10000rpm. 7200rpm hard disk has become mainstream.

3. Cache

Cache (Cache) is the place where the hard disk exchanges data with the external bus. Simply put, the bigger cache capacity on the hard disk the better, large capacity cache is good at improving the speed of the hard disk, the hard disk cache capacity in current market is usually 2MB ~ 8MB.

4. Average Seek Time

Average seek time (Average Seek Time) refers to the track of the time that the hard disk head to the data, in milliseconds (MS). Average search time is generally between 5ms ~ 13ms.

5. Hard disk data transfer rate

Hard disk data transfer rate (Data Transfer Rate), also known as throughput rate, It means after the head positioning, the speed that hard disk to read or write data.

6. Mean Time Between Failure, MTBF

MTBF refers to the longest time that the hard disk from the start to the failure. the unit is an hour. General hard disk MTBF is at least 30000 — 40000 hours. This indicator is not available in the general product ads or common technical features, but can be checked in a specific production of the company’s Web site.

## What Is Panoramic Camera

Panoramic camera, as the name suggests, is a wide range of surveillance cameras, it can be divided into single-lens fish-eye camera and multi-lens stitching camera according to different structures. Taken the angle of view between multiple lenses, the installation location and other factors into consideration, the general price of Multi-lens stitching camera is more expensive, rarely used in the project, so the fish-eye camera has become a representative of the panoramic camera.

Fish-eye cameras rely mainly on fish-eye lens to achieve a wide range of monitoring, the biggest feature is the formation of the image into a circle, to achieve 180 degree omni-directional coverage, in order to clear the overall situation. In order to realize 180 degree omni-directional monitoring, a surveillance camera needs at least two cameras to be mounted back-to-back. Unless there is a special adjustment of the angle of view, there is a blind spot at the bottom of the camera. The larger the focal length of the camera, When a moving object moves from the field of view of one camera to the field of view of another camera, it is difficult to form a complete image association, and it is likely to cause visual disturbances. This is the two main advantages of the fish-eye camera compared to the common camera.

Compared to the ordinary camera, since the fish-eye camera exits advantages, why it has not been eye-catchy in the market?

In fact, the application of fish-eye cameras have been in the panoramic monitoring, but it is hard to meet people’s expectations in capturing details. As the fish-eye lens is ultra-short focal length lens, although the field of view is large enough through the fish-eye lens formed by the screen, but the detail object in the picture will be very small; In addition, the circular viewing angle through the fish-eye lens does not meet the human eye viewing habits, and the quality of side area is badly distortion, missing a lot of details.

The development trend of fish-eye camera:

Until recent years, with the distortion correction technology matures and the use of EPTZ technology, the appearance of the fish-eye camera on the details began to meet people’s expectations, enhance the practicality of the screen before they gradually enter the public’s vision. The so-called distortion correction is to show normal display instead of distortion circular image as much as possible; with EPTZ function, you can zoom in and move the image to achieve the effect similar to the PTZ operation, which is easy to view some of the details.

In addition to distortion correction and EPTZ, are there any other ways to improve the usefulness of its picture? The answer is, of course, yes.

The first method is to improve the overall screen resolution. In the panoramic images, the more peripheral images, the same number of pixels carried by the broader monitoring range, the content required to show more, so the higher the resolution of the fish-eye camera, the more pixels Point to show the same scene with more details. with the EPTZ function more and more to improve the practicality of the screen. Currently on the market, the fish-eye camera resolution is mainly concentrated in the 3 million to 5 million, with 4K ultra-high-definition cameras into people’s field of vision, ultra-high definition fish-eye camera is inevitable.

But to improve the resolution is not just a simple upgrade Sensor and lens, ISP processing, coding, the network needs to be considered, and, the high-resolution fish eye camera has to be more strict than the ordinary fish eye camera in the requirements of corresponding structure and process.

The second method is the fish ball with the ball machine to achieve fish ball linkage. Fish-ball linkage is an upgraded version of gun-ball linkage, through the fish-eye camera to monitor the overall situation, once the suspicious target linkage ball machine to enlarge the target. Compared with the gun ball linkage, fish ball linkage of the global monitoring range is larger; compared to the fish-eye camera’s own EPTZ, the ball machine magnification effect is more clear.

Because of the seriously distorted image formed by the fish-eye camera, it is necessary to provide a more accurate linkage algorithm than the gun-ball linkage.

The value of monitoring should be landing on the practicality, poor practicality with fancy features will not be recognized by the user, so the two methods to improve the usefulness of the screen will be the key points of a new generation of fish-eye cameras.

## Why Should You Be Industry Certified

Sure you can be certified by a manufacturer, but what about in the industry?. Manufacturer certification shows you are proficient and trained in their product. What about your proficiency as a whole?

Sure you can be certified by a manufacturer, but what about in the industry?. Manufacturer certification shows you are proficient and trained in their product. What about your proficiency as a whole?

An Integrator and installer typically need to certified before the can carry a specific brand. Manufacturers like Pelco, Samsung and Panasonic have their own certification programs that cover installation, configuration, maintenance and training of their product with the basic premise that the individual or company already knows the basics. The basics, however, can be different from market to market due to city codes. Some have not had the pleasure of installing cabling in rigid conduit and the costs associated with it. Others have never installed equipment in an explosion proof environment.

How many of you came into another surveillance companies prior installation and wondered how anything can possible work? How many have seen a multitude of problems from sloppy wiring, poor terminated ends, power supplies lying on the floor, wrong cable type, cable too long, multiple splices, multiple splitters’, cameras in areas the should have housings but don’t, no site plan or many other poor practices? For the end-user this usually means system problems and service calls to correct something that should have been done correctly the first time.

There are several organizations out there that certify based on security principals and knowledge but not on real world practice. UL Certification for alarm system installation comes the closest but for alarm systems only. No one had a similar certification for video surveillance or access control, until now. An organization called NAVSAC (National Association of Video Surveillance & Access Control) has a multi-level program that combines knowledge and practical experience with an inspection service. Level 1 is a basic proficiency exam with a company background check. NAVSAC verifies incorporation, owner credentials and insurance information. Level 1 must be in business a minimum of 1 year prior to applying. Level 2 takes it 1 step further by conducting interviews and questionnaires with clients. The applicant then chooses 3 clients for inspection varying in complexity and design. The goal is to measure proper installation techniques, design and engineering, cleanliness, termination, site plans and quality. Level 2 also requires a minimum of 2 support staff, support ticketing system and documented polices for providing support.

Each levels requirements increase in difficulty and time-in the industry in order to advance. The most amazing thing that attracted me to look closer was the promotion of members. Typically most organizations you will get a certificate and a directory listing. With NAVSAC, they actively promote their members through the web and other outlets. The concept promotes pride in being a true industry professional and therefor the consumer should know who you are. They offer additional services such as web design and marketing specific for the industry following strict guidelines for honest and ethical marketing. The additional services help professional companies get noticed and weed out the opportunists.

Furthermore, consumers can go to www.navsac.org and verify all members credentials and experience and can see photos of previous installations. NAVSAC also provides arbitration services if a customer should have an issue with a member.