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Magnetism has long been underrated compared to its partner electricity. Magnetism forms the heart of nearly every electronic device that we see these days. Be it the good old electric motor or the transformer.

Televisions, CRT monitors, DC Motors, various measuring instruments, etc make use of permanent magnets in their working and electromagnetism seems to be virtually everywhere. While permanent magnets have typically been thought of made of iron, recent years have seen the emergence of permanent magnets made of alloys of rare earth metals.

Rare earth magnets are much stronger than typical magnets made of ferrite or alnico, giving them a huge area of potential applications

Widening the field of Rare Earth Magnets

The name ‘rare earth magnets’ misleads many into thinking that they are very rare and precious, but in fact ‘rare earth’ refers to a class of metals, namely the lanthanide series metals, not particularly rare in the earth’s crust. Rare earth metals are ferromagnetic, that is, they can be magnetized, like Iron. But in normal conditions their magnetism manifests in very low temperatures.

As a comparison, the magnetic field generated by rare earth magnets is around 1.4 to 1.5 Tesla (unit of magnetic field) while that generated by typical ferrite or alnico magnets is around 0.5 to 1 Tesla. There are two major kinds of rare earth magnets currently prevalent.

Samarium-Cobalt was the earlier standard, somewhat more expensive and less powerful compared to Neodymium magnets now used. Neodymium is very powerful and affordable. The high magnetic field strength and magnetic anisotropy of rare earth magnets, along with their affordable price, enables them to have widespread application. Some common applications include:

–          Hard disk drives in Computers
–          Headphones and speakers
–          Bicycle dynamos
–          Self-powered flashlights, that use a rare earth magnet to generate electricity for operating the light
–          Permanent magnet motors
–          Security systems
–          Mag-lev trains
–          Industrial uses like magnetic separation, retrieval, etc
–          In miniatures, toys, etc.

Rare Earth Magnets – Beware!

With great power comes the ability to be dangerous, and it is the same with rare earth magnets.

Rare earth magnets have hazards unseen in typical magnets. Larger magnets are capable of causing serious injuries, even broken bones, if some limb or part of the body gets stuck in between 2 magnets or a magnet and a metal surface.

Also, these magnets should be kept well out of the reach of small children. If ingested, they may be very dangerous, even fatal. Apart from the danger of physical injury, rare earth magnets should also be kept at a safe distance (namely 12 cm) from devices using magnetic storage, like hard disks, credit cards, etc.

Ever since the Stone Age man first observed small pieces of Lodestone get attracted to each other, magnets have held man’s imagination. Magnetism, to the ancient man, was magic, something that he couldn’t explain.

The science behind it was eventually discovered and since then magnets have become integral to working of nearly every electrical or electronic device we use. While the general idea is that magnets should be made of iron, very permanent magnets are Alnico.  Not named after an Italian founder, Alnico actually stands for Aluminium, Nickel and Cobalt, the alloys of which, along with Iron, make up the Alnico magnet.

Alnico magnets are generally stronger than typical Ferrite ones, making them ideal for various applications. Until the discovery of Rare earth magnets, Alnico magnets used to be the strongest type of permanent magnets.

Deep in the core of Alnico magnets

Alnico magnets are the strongest types of permanent magnets, second only to Rare Earth Magnets like Neodymium and Samarium-Cobalt. The strongest factors in the favour of Alnico magnets are their extremely good temperature resilience, high residual induction and strong enough magnetic fields generated.

Primary ways of manufacturing Alnico magnets include casting and sintering. The magnets manufactured using casting can be made into any desired shape and size, horseshoes, etc. Sintered magnet, however not very powerful, give very good mechanical characteristics not found in other magnets.

Alnico give magnetic field strength upto around 0.5 Tesla (Unit of magnetism), much stronger than normal Ferrite magnets. Some types of Alnico magnets are also isotropic, hence could be magnetized in any direction, while others are anisotropic. A great advantage of Alnico magnets is that they are very stable.

And if handled with care, can be safer to use as opposed to Rare-earth magnets which have to be handled very carefully in order to avert mishaps or accidents.

The wide spreading field of Alnico magnets

Due to the properties of Alnico magnets, they are in widespread application around the industry. They are relatively strong, inexpensive and safe. They are widely used in industry as well as consumer goods, anywhere where strong permanent magnets are needed. Some of the common applications of Alnico magnets include:

–          Electric Motors
–          Microphones
–          Loudspeakers/ Speakers
–          Rotating machinery
–          Holding devices
–          Instruments
–          Sensing equipment
–          Travelling wave tubes, etc

While Alnico magnets still have a stronghold in the industry, it is soon being replaced by the higher strength and higher energy rare-earth magnets.

A Ferrite magnet is a category of permanent magnet. Its major constituent is Iron (III) oxide. It is the simplest of all existing permanent magnets and therefore also lower in cost compared to them. They are also used as magnetic cores for transformers among other applications. They are hard and brittle.

A Ferrite magnet is a ceramic and also a magnet therefore it attracts ferromagnetic materials like itself, and may attract or repel other magnetic materials depending on their magnetivity. They are classified broadly into two categories depending on their magnetic properties – hard ferrites and soft ferrites.

These categorizations do not depend on the hardness or softness of the magnets but rather on their magnetic coercivity with soft corresponding to low coercivity and hard corresponding to high coercivity.  All Ferrite magnets degrade in magnetic properties linearly with temperature, that is, as the temperature is increased the strength of the magnet decreases.

The strength of Ferrite magnets is measured in Tesla. Tesla is the unit of measurement of the strength of a magnet i.e. its magnetic field and is named after the Serbian scientist Nikola Tesla.

Manufacturing Ferrite Magnets in the industry

The manufacture of Ferrite magnets is an elaborate process involving pressing, sintering, injection molding, special machining etc. Ferrite powder is first pressed and then the pressed product is heated in a sintering furnace below its melting point to form a solid magnet.

Pressing can be of two types – wet and dry. A wet pressed magnet has superior magnetic properties as compared to a dry pressed one but the latter shows higher physical tolerance. Sintering is the process that creates the solid magnet out of the pressed powder by heating the latter to a high temperature. It takes place in a specific atmosphere such as one with a shortage of oxygen.

Ferrite is brittle, and therefore can easily chip or crack. To machine this material it is imperative to use special machining techniques. While magnetizing them no special care is required other than the fact that since large blocks of Ferrite magnets are pretty strong, care should be taken to ensure that they don’t snap towards each other.

The applications of Ferrite magnets

Ferrite magnets are used in electronic inductors (in applications such as switched-mode power supply(SMPS)), transformers, electromagnets, motors, magnetic couplings, for sensing, loudspeakers, holding-magnet systems, crafts, magnetic therapy, novelties, and toys etc.

It is an important component used in magnetic tapes and in computer memories. It also finds use in electromagnetic instrument pickups because of its low cost and high output.

Replication is the copying of information to multiple computer systems or databases in a way that ensures consistency of the information across systems.

Synchronous Replication is a data replication technique between databases and file systems which delivers fastest recovery of data without any significant data loss, while providing protection against problems related to database integrity. This ensures that data is replicated between systems efficiently without any losses.

Synchronous replication creates a remote copy of the data, which is an exact mirror image of the primary copy, when the primary copy is updated. The system with the primary copy proceeds after waiting for the data recording to have completed on the duplicate system.

In synchronous replication, only after completion of an input/output operation is confirmed at both the primary and mirrored sites, is the update operation considered complete.   A rollback takes place at both the locations when incomplete operation takes place which ensures that the remote copy is an exact copy of the primary.

The advantages and disadvantages of synchronous replication

There are some advantages for synchronously replicating data, while quick data recovery is one of the major of them. If there is a disruption of the operation at the primary site, the operations at the remote site can begin at that very instant, at the point where the primary site stopped. The operations which are being processed at that instant are the only ones which are at a risk of being lost.

However, there are some disadvantages as well for synchronous replication when the main one is the large response time, which arises because the primary system has to wait for the secondary system before it can proceed.

Thus, because of the increased response time and communication delays, synchronous replication is often impractical unless the secondary system is physically located close to the primary system. The primary enterprise storage transport protocol is Fibre channel.

Theoretically this fibre channel can extend up to a maximum of 200 kilometers.  However, the time lags become a problem as the propagation delays increases with the increasing distance. Propagation delays force the system to pause and wait for confirmation of every storage operation at the primary and the remote sites.

These delays cause significant system slow down. Considering the response time and other factors, the practical distance for synchronous replication is marked at 35 kilometers to 50 kilometers for a busy system.

The application of synchronous replication

The most commonly found example of the use of synchronous replication is in Google Apps. Google Apps store customer information in two data centers at the same time, so that if by chance one of these centers fails, Google can instantly transfer data over to the other center since this has also been reflecting the actions taken by the customer all along.

This concept is applied to the entire Apps suite as well as Gmail including Google Calendar, Google Docs and Google Sites!

People all over the world are consumers of several basic products, but in different forms. Everyone, no matter where they are on the face of the planet or how old they are has the need to eat, to drink and to breathe.

These are our most natural urges or instincts which are indeed the commons of everybody. However, as time progressed and men became more connected with their fellow brothers, another need that is almost natural came to take a nice place in the human needs list. This is the need to know.

People don’t just want, they need information. Curiosity is the name of the game and collecting information is how you do it. The information collected is ought to be stored somewhere as the human brain can only store a limited quantity of data. So we have invented computers to assist us in storing and protecting our beloved information.

There are several methods available to use today for increasing the protection of the information we have. Synchronous replication is one of them. The more information you have and the more changes you perform on it, you’ll need a system to guarantee you full protection.

Synchronous replication here, there and almost everywhere

A common system which was and still is in use for replicating your information – whether you’re a private home computer user or a head of a department in a big corporation – is the backup tape. Like in synchronous replication a backup is done in a pre set date and time by placing a backup tape in the main server, copying the data and removing it for storage in a different location.

However, the tapes don’t provide you, the user and data owner, a full protection and a complete confidence that your information is one hundred percent protected. Today’s gigantic black-hole of a media world requires a more stable and ensuring system.

Synchronous replication can answer that call. First of all, it insures that the information replicated will be equal to the information on the main server, and this actually means that there is no chance whatsoever for you to lose even a comma from your data files. However, you should take into consideration that the synchronous replication system works best under very certain conditions.

Due to its relatively high costs it’s recommended that you’ll do the math and jump in only if you’re a financially big company or corporation. Another factor is the distance.

Note that this system is wonderful only for a short distance between the main servers to the storage protected location.

Synchronous replication – still a safety net

Even with the slight disadvantages, this highly sophisticated method for replication and protection of important and valuable information known as synchronous replication can still be used as a safety net for many firms and large corporations and enterprises.

One of the most important things for a brand, company or institute is its data. The data is very important for maintaining the records, transactions or information. Any company or institute cannot afford to lose them under any conditions.

A lot of measures are taken to protect them from internal and external threats which are increasing day by day. These threats can range from virus attacks to faulty power grids. Thus companies or institutions have to think of an idea for successful disaster recovery. And the most efficient and effective recovery option will be replication of data to a secondary site.

Replication of data helps in a number of ways such as reducing the time of system maintenance and testing of applications. There may be two kinds of this replication processes- Asynchronous replication and Synchronous replication.

The efficiency of asynchronous replication

Synchronous systems are used for shorter distances whereas Asynchronous systems are used for longer distances. In terms of data loss, Asynchronous systems may or may not lose some data during transaction unlike synchronous systems where we can get an exact copy of the source and destination files.

However, asynchronous replication systems ensure a rapid restart-able data image.  In terms of distance, asynchronous mode of data replication can be used for almost any distance. The distance of the secondary site could range from hundreds to thousands of miles from the source site.

The reason behind this is the absence of propagation delay involved in confirming transactions which is actually the waiting time to update the replication site and its confirmation to return. In terms of data integrity, sequence stamps or codes are used to ensure exact data replication on asynchronous replication systems.

One of the most important advantages of asynchronous replication systems is that it is less costly than synchronous mode of replication and generally suites the organization that can tolerate being down for some minutes to hours until the last few transactions are restored. Also if the company cannot tolerate the performance impact of synchronous mode of replication, asynchronous systems could be a good idea.

Choosing asynchronous replication

We can say that both synchronous and asynchronous replication processes have its own merits and demerits and it’s completely the specific needs of the company which can determine which technique to use.

A complete assessment of the business has to be done before making any choices. The decision is quite complex and generally depends on different aspects of the company like assessments of potential risks and business impact analysis.

However, choosing asynchronous replication is highly advisable when all the aforementioned factors take place in an enterprise.