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Articles (1-2 of 2 total entries)
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| KVM over IP |
General |
| Thursday- July 31, 2008 @ 09:05:36 EAT |
General |
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KVM switch:
KVM switch (with KVM being an abbreviation for Keyboard, Video or Visual Display Unit, Mouse) is a hardware device that allows a user to control multiple computers from a single keyboard, video monitor and mouse. Although multiple computers are connected to the KVM, typically a smaller number of computers can be controlled at any given time. Modern devices have also added the ability to share USB devices and speakers with multiple computers. Some KVM switches can also function in reverse - that is, a single PC can be connected to multiple monitors, keyboards, and mice. While not as common as the former, this configuration is useful when the operator wants to access a single computer from two or more (usually close) locations - for example, a public kiosk machine that also has a staff maintenance interface behind the counter, or a home office computer that doubles as a home theater PC.
USE:
A user connects a monitor, keyboard, and mouse to the KVM device, then uses special cables (generally USB and VGA ) to connect the KVM device to the computers. Control is switched from one computer to another by the use of a switch or buttons on the KVM device, with the KVM passing the signals between the computers and the keyboard, mouse and monitor depending on which computer is currently selected. Most electronic devices also allow control to be switched through keyboard commands (such as hitting a certain key, often Scroll Lock, rapidly two or three times).
Devices differ in the number of computers that can be connected, with anywhere from two up to 64 computers possible. Enterprise-grade devices can also be daisy-chained to allow even greater numbers of computers to be controlled from a single set of a keyboard, visual display unit and mouse.
A KVM switch is useful where there are multiple computers, but no need for a dedicated keyboard, monitor and mouse for each one. They are frequently used in data centers where multiple servers are placed in a single rack with a single keyboard, monitor and mouse. A KVM switch then allows data center personnel to connect to any server in the rack. A common example of home use is to enable the use of the full-size keyboard, mouse and monitor of the home PC with a portable device such as a laptop, tablet PC or PDA.
Passive and Active (Electronic) switches
KVM switches were originally passive, mechanical devices based on multi-pole switches and some of the cheapest devices on the market still use this technology. Mechanical switches usually have a rotary knob to select between computers. KVMs typically allow sharing of 2 or 4 computers, with a practical limit of about 12 machines imposed by limitations on available switch configurations. Modern hardware designs use active electronics rather than physical switch contacts with the potential to control many computers on a common system backbone.
One limitation of mechanical KVM switches is that any computer not currently selected by the KVM switch does not 'see' a keyboard or mouse connected to it. In normal operation this is not a problem, but while the machine is booting up it will attempt to detect its keyboard and mouse and either fail to boot or boot with an unwanted (e.g. mouseless) configuration. Thus mechanical KVM switches are unsuitable for controlling machines which may reboot automatically e.g. after a power failure.
Most active (electronic) KVM devices provide peripheral emulation, sending signals to the computers that are not currently selected to simulate a keyboard, mouse and monitor being connected. These are used to control machines which may reboot in unattended operation. Peripheral emulation services embedded in the hardware also provides continuous support where computers require constant communication with the peripherals.
Another problem frequently encountered with mechanical devices is a failure for all terminals to properly make contact, requiring some 'wiggling' of the knob to correct patchy colors on screen or unreliable peripheral response.
Software alternatives
There are software alternatives to a hardware KVM switch such as Synergy, Virtual Network Computing (VNC), teleport or the non-free Multiplicity and PC Anywhere, which do the switching in software and forward input over standard network connections. This has the advantage of reducing the number of wires needed, and the screen-edge switching it provides makes it easier to forget that you are using two computers. However, there are some disadvantages. Software alternatives typically require additional software to be pre-loaded onto each one of the target servers or computers to allow clients to remotely attach to. They also can not be used when the host Operating System is not installed yet or has not started: operating system installations are thus not possible nor is access to a computer's BIOS or other built-in configuration areas. Finally, the software alternatives can be difficult or impossible to access if the computer is very busy or has stopped responding to network connections.
Remote KVM devices
There are two types of remote KVM devices that are best described as Local Remote and KVM over IP.
Local Remote
Local Remote KVM device design allows users to control computer equipment up to 1000 feet away from the user consoles (keyboard, monitor and mouse). They include support for standard category 5 cabling between computers and users interconnected by the switch device. In contrast, USB powered KVM devices such as the KVM2USB [1] are able to control computer equipment using a combination of USB, keyboard, mouse and monitor cables of up to 5 meters.
Category 5 based KVM device communication uses proprietary protocols across what can be considered a "closed loop" local area network infrastructure. In contrast to remote over IP devices, users operate computers in "real time" because there is no noticeable latency in communication between user consoles and the computers.
Small interface devices at the computers connect to the keyboard, VDU and mouse ports of the computer. They convert these signals to a format suitable for category 5 cable and transmit this data to the user stations that decode it into normal analog signals suitable for the peripherals. Similar devices exist for KVM over IP that only support transmitting the signals at distances of thirty to fifty feet. While interface, switch, and user devices are interconnected using category 5 cabling and can be patched through non-active patch panels, the data signals are not the equivalent of ethernet (see Tron: Category 5 - Ethernet vs KVM Networks [2]) so care must be taken not to cross connect these KVM components to ethernet switches.
Local remote KVM systems can support over 256 access points with access to over 8000 computers. The closed loop backbone is inherently secure and the long distance connectivity allows users and computer equipment to be distributed across many different locations throughout a facility. Where users need to manage the connected computers from off site locations, local remote KVM devices are configured with Remote over IP KVM support.
KVM over IP
KVM over IP devices use a dedicated microcontroller and potentially specialized video capture hardware to capture the video, keyboard, and mouse signals, compress and convert them into packets, and send them over an Ethernet link to a remote console application that unpacks and reconstitutes the dynamic graphical image. This KVM over IP subsystem is typically connected to a system's standby power plane so that it's available during the entire BIOS boot process. These devices allow multiple computers to be controlled remotely across a wide area network, local area network or telephone-line using the TCP/IP protocols. There are performance issues related with LAN/WAN hardware, standard protocols and network latency so user management is commonly referred to as "near real time". And, remote KVM over IP devices offer much smaller matrix frameworks.
Access to most remote or "KVM" over IP devices today use a web browser but proprietary viewer software can increase performance. A consideration of the viewer software relative to a browser based application is the area of ActiveX or Java security. Well formed implementations can be found across the major vendors today, yet there are many entry-level implementations that may not be as robust when it comes to security, performance and reliability. Important to note is that many of the stand-alone viewer software applications provided by many manufacturers are also reliant on ActiveX or Java. In addition, each major manufacturer is free to use various licensing mechanisms, some based on numbers of target devices, some based on numbers of users, and some based on numbers of sessions.
In comparison to conventional methods of remote administration (for example Virtual Network Computing or Terminal Services), a KVM switch has the advantage that it doesn't depend on a software component running on the remote computer, thus allowing remote interaction with base level BIOS settings and monitoring of the entire booting process before, during, and after the operating system loads. Modern KVM over IP appliances or switches typically use at least 128-bit data encryption securing the KVM configuration over a WAN or LAN (leveraging SSL, and thus MD5 or AES)
KVM over IP devices have been implemented in many different ways. For the graphics capture portion, PCI based KVM over IP cards use a variation of a technique known as screen scraping where the PCI bus master KVM over IP card would access graphics data directly from the graphics memory buffer. In these cases, the PCI card must know which graphics chip it is working with, and what graphics mode this chip is currently in so that the contents of the buffer can be interpreted correctly as picture data. Newer techniques such as those used by OPMA management subsystem cards and other implementations obtain the video data directly from the graphics chip using the industry standard DVI bus. There are also a variety of ways to emulate the keyboard and the mouse remotely, but newer implementations emulate USB based keyboards and mice using the management controller.
From Wikipedia, the free encyclopedia
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| Understanding Raid |
General |
| Thursday- February 07, 2008 @ 12:51:07 EAT |
General |
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What is RAID?
The acronym RAID means Redundant Array of Independent (or Inexpensive) Disks. When originally developed at the University of California at Berkeley in 1987, the word was “Inexpensive,” referring to the fact that it was basically an array (or group) of relatively inexpensive disk drives grouped together in such a way that to the computer it appeared to be one very large (and thus very expensive) hard drive. Comparatively speaking, the cost of hard drives is now much less, so when you mention “RAID,” your colleague is most likely thinking “Redundant Array of Independent Disks.” Five levels of RAID were originally defined, each providing different trade-offs in features and performance.
Why Is RAID Important?
There are two main purposes to RAID – a method of storing the same data in different areas (which is where the word “Redundant” comes in), and a way to speed up and stabilize your computer’s performance. Through trial and error, the Berkeley group developed different types of RAID that balanced the need for increased performance with the desire for more reliability in data storage.
One might think that with today’s high-speed and large capacity drives, RAID would no longer be relevant. However, transfer rates and capacity of current individual drives cannot keep pace with the continuingly increasing need for data storage capacity and high speed data access. RAID is still the best answer to the question of how to provide quick access to a lot of stored data at a reasonable cost, with the added plus of data protection.
RAID is not necessarily easy to install and maintain on your own computer system, but if you have ever had a hard drive crash, you know how costly in time and effort it is to restore the data on that hard drive. Current web hosting packages usually include RAID protection of some kind, which is reflected as the percentage of “uptime” a web host claims to offer.
What Types of RAID Are Available?
There are a number of variations of RAID, each with its own individual advantages and disadvantages, but the ones listed below are the basic building blocks for other variations.
1. RAID Level 0 is based on a method called “striping,” which breaks all the data on your computer into smaller chunks of data that are placed across all available disk drives. Its biggest advantage is that the small packages of data scattered across a number of drives can be very quickly pulled together into a coherent whole.
The biggest disadvantage to RAID 0 is that even if just one of the drives in the system fails, you in effect lose all of your data, since at least part of it would have been stored on the drive that has failed.
2. RAID Level 1 introduces the benefit of “mirroring,” or copying all of your data onto at least one another drive, perhaps even onto many other drives. This ensures that your data will be duplicated in whole on at least one other hard disk, so if your data is lost in a disk failure, there is at least one extant copy immediately available. RAID Level 1 documents usually have enhanced read times as well. If fault tolerance is the key benefit you are looking for, RAID 1 is the most basic level that offers this feature.
The biggest disadvantage to RAID 1 is the cost of having additional disk drives containing the mirror of your data.
3. Combination of RAID Levels 0 and 1
A combination of both RAID 1 0 employs mirroring and striping methods – making sure you will not lose all your data if a hard disk fails and also giving you the spanning capacity of multiple hard disks – all at speeds faster than possible from a single disk. This combination offers the best of both worlds.
4. And there is also RAID 5, which is often viewed as the ideal mix of good performance, good fault tolerance, high capacity and storage efficiency. Reason being that RAID 5 stripes both data and parity information across three or more drives.
In today’s web hosting packages, some form of RAID is usually included as a standard part of the package, so do not be surprised if no specific mention is made of RAID when you sign with a web host. The presence and effectiveness of a web host’s RAID system is very closely represented by the host’s server uptime. High server uptimes (not to be confused with connection uptimes) typically indicate that a well-managed RAID system is in place.
If you decide that an individualized RAID setup is necessary for your website itself, collaborate extensively with your web host before purchasing the necessary equipment. There are various hybrids of RAID implementations which really are just enhancements of the basic RAID arrays described above.
Is RAID Hardware Better Than RAID Software?
When you are deciding between a hardware versus software RAID solution, the key is to look at the levels of RAID the option provides.
Software RAID usually supports RAID 0 and 1 (speed through striping and fault protection through mirroring). Hardware RAID, however, will include a number of additional data recovery tools – for example, a SCSI-based RAID card will support many RAID levels, each providing a different combination of speed and data protection.
In essence, software control is cheaper and easier to maintain but takes up server processor resources. On the other hand, RAID hardware does the work separately from the server processor, but is more expensive overall.
Do I Need RAID?
Even if your web host provides RAID protection, the best web host can fail – no one can realistically promise 100% uptime. Despite this, as long as the web host has a good uptime rate, most websites do not choose the added expense of their own RAID system.
Generally speaking, the type of websites that may need additional RAID protection are those that deliver critical or time-sensitive news or information on their websites; or those that maintain a database that has large file sizes or high recall rates which are cumbersome or slow to restore in the event of web host hardware failure.
You probably do not need a RAID system of your own if all you do is maintain static textual and graphic content, such as on a company website or a photo album. RAID usually makes most sense for businesses whose websites play a significant role in their profitability. Some examples include websites that need to store large amounts of data and want it to be quickly and reliably available to them, such as industries requiring high bandwidth, like video production and editing applications, image editing, and prepress applications.
What is the Relationship Between RAID and the Backup of Data?
Whether you decide to install RAID on your computer or not, the most important thing to remember is that RAID is NOT a replacement for a systematic and regular backup process for your computer system. You should be keeping backup copies of all your data locally and making sure that your web host also does regular backups of data.
Take responsibility for ensuring that your data is backed up as frequently as you need (daily backups are of course the ideal) no matter what type of RAID you or your web host maintain. RAID provides improved data storage capabilities and increased fault tolerance, but it is not a substitute for a regular backup procedure in the ultimate goal of keeping all the hard work you have done on your website safe and secure.
Boris Mordkovich is the Director of Operations for MordComm, Inc., a New York-based firm that develops and operates online ventures that help small to mid-size businesses succeed in their online ventures. Their properties include:
AdWatcher: Ad Monitoring & Tracking - is a revolutionary ad tracking system that helps businesses get more customers out of their advertising campaigns and save money normally wasted on ineffective marketing by tracking the exact Return on Investment for all of their online ad campaigns for less than $0.55c/day.
PayPerClickUniverse: Pay Per Click Search Engines Guide - unbiased reviews, ratings, articles, tools and other information on the top pay per click search engines, along with special deals and a list of 100 search engines that offer free money just for signing up.
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