Microsoft Exchange Server 2010: High availability strategies

The strategies Microsoft offers for creating highly available Microsoft Exchange mailboxes have evolved over the years.

Jaap Wesselius

Ever since Exchange Server 5.5, Microsoft has offered Windows Clustering as an option for creating a highly available Exchange mailbox environment. There are two server nodes available in a typical shared-storage cluster environment. Both are running Exchange Server and both servers are connected to a shared storage solution.

In the early days, this shared storage was built on a shared SCSI bus. Later on, it typically used storage-area networks (SANs) with a Fibre Channel or iSCSI network connection. The important part was the shared storage where the Exchange Server databases were located.

Only one server node is the “owner” of this shared data. This node provides the client services. It’s also known as the active node. The other node isn’t able to access this data, and is therefore the passive node. A private network between the two server nodes is used for intra-cluster communications, such as a heartbeat signal. This lets both nodes determine the cluster state and ensure the other nodes are still alive.

Besides the two nodes, it creates an “Exchange Virtual Server” as a cluster resource. This has nothing to do with virtual machines. This is the resource to which Outlook clients connect in order to access their mailboxes. When the active node fails, the passive node takes over the Exchange Virtual Server, which then continues to run. Although users will notice a short downtime during the failover, it’s an otherwise seamless experience. No action is required from the user.

Although this solution offers redundancy, there’s still a single point of failure—the shared database of the Exchange server. In a typical environment, this database is stored on a SAN. By its very nature, a SAN is a highly available environment. When something does happen to the database, though, such as a logical failure, the database is unavailable for both nodes. This results in total unavailability.

Exchange database replication

With Exchange Server 2007, Microsoft offered a new solution for creating highly available Exchange environments: database replication. Database replication creates a copy of a database, resulting in database redundancy. This technology was available in three flavors:

• Local Continuous Replication (LCR): This approach creates a copy of the database on the same server.
• Cluster Continuous Replication (CCR): This creates a copy of the database on another node in a Windows failover cluster (there can only be two nodes in a CCR cluster).
• Standby Continuous Replication (SCR): This came with Exchange Server 2007 SP1. It creates a copy of a database on any other Exchange Server (not necessarily in the cluster). This isn’t meant for high availability (HA); it’s more for disaster recovery.

This is how database replication works in a CCR clustered environment. Exchange Server 2007 is installed on a Windows Server 2003 or Windows Server 2008 failover cluster. There’s no shared storage in use within the cluster. Each node has its own storage. This can be either on a SAN (Fibre Channel or iSCSI) or direct-attached storage (DAS)—local physical disks.

The active node in the cluster services client requests, and Exchange Server uses the standard database technology with a database, log files and a checkpoint file. When Exchange Server is finished with a log file, it’s immediately sent to the cluster’s passive node. This can either be via a normal network connection or via a dedicated replication network.

The passive node receives the log file and checks it for errors. If it finds none, the data in the log file is relayed to the passive copy of the database. This is an asynchronous process, meaning the passive copy is always a couple of log files behind the active copy, so information is “missing” in the passive copy.

In this environment, all messages—even internal messages—are sent via a Hub Transport server. The Hub Transport server keeps track of these messages in a CCR environment. It can therefore send missing information (that the passive node actually requests) to the passive copy of the cluster in case of a cluster failover. This is called the “Transport Dumpster” in a Hub Transport server.

This kind of replication works very well. CCR replication is quite reliable, but there are a couple of potential drawbacks:

• An Exchange Server 2007 CCR environment runs on Windows Server 2003 or Windows Server 2008 clustering. For many, this adds too much complexity to the environment.
• Windows Server 2003 clustering in a multi-subnet environment is nearly impossible, although this has improved (but still isn’t perfect) in Windows Server 2008 failover clustering.
• Site resilience isn’t seamless.
• CCR clustering is only possible in a two-node environment.
• All three kinds of replication (LCR, CCR and SCR) are managed differently.

To overcome these issues, Microsoft dramatically improved the replication technology. It also reduced the administrative overhead. It achieved this by completely hiding the cluster components behind the implementation of Exchange Server 2010. The cluster components are still there, but the administration is done entirely with the Exchange Management Console (EMC) or the Exchange Management Shell (EMS).

DAG continuous replication

In Exchange Server 2010, Microsoft introduced the concept of a database availability group (DAG). This is a logical unit of Exchange Server 2010 Mailbox Servers. All Mailbox Servers within a DAG can replicate databases to each other. A single DAG can hold up to 16 Mailbox Servers and up to 16 copies of a database.

The idea of multiple database copies in one Exchange organization is called Exchange Mobility. There is one database on multiple servers, each instance of which is 100 percent identical and thus has the same GUID.

With a DAG in place, clients connect to an active database. This is the database where all data was stored initially. New SMTP messages, either from outside or inside the organization, are stored in this database first.

When the Exchange Server has finished processing information in the database’s log file, it replicates the file to other servers. You can assign the servers that receive a copy of the database. The log file is inspected upon receipt and if everything is all right, the information in the log file is dropped into the local copy of the database.

In Exchange Server 2010, all clients connect to the Client Access Server, including all Messaging Application Programming Interface, or MAPI, clients such as Microsoft Outlook. Supported Outlook clients in Exchange Server 2010 include Outlook 2003, Outlook 2007 and Outlook 2010.

So the Outlook client connects to the Client Access Server, which then connects to the mailbox in the active copy of the database. Unfortunately, this is only true for mailbox databases. When an Outlook client needs to access a public folder database, the client still accesses the mailbox server directly.

When the active copy of a database or its server fails, one of the passive copies of the database becomes active. You can configure the failover order during the database copy configuration process. The Client Access Server automatically notices the failover and starts using the new active database. Because the Outlook client is connected to the Client Access Server and not directly to the database, a database failover is fully transparent. Messages such as, “The connection to the server was lost,” and, “The connection to the server is restored,” simply don’t appear anymore.

When building a highly available mailbox server environment in a DAG, there’s no need to build a failover cluster in advance. You can add additional mailbox servers to the DAG on the fly. However, for the DAG to function properly, you’re still using some failover clustering components. These are installed during the DAG configuration. You do all DAG and database copy management via the EMC or the EMS. You no longer have to use the Windows Cluster Manager.

The DAG with database copies is the only HA technology Exchange Server 2010 uses. Older technologies such as SCR, CCR and SCR are no longer available. The traditional single-copy cluster with shared storage is no longer supported, either.

Configuring a DAG is no longer limited to a server holding just the mailbox server role. It’s possible to create a two-server situation with the Hub Transport, Client Access and Mailbox Server roles on both servers, and then create a DAG and configure database copies.

However, it isn’t an HA configuration for the Client Access or Hub Transport servers unless you’ve put load balancers in front of them. You can’t use the default Windows Network Load Balancing in combination with the failover clustering components. Nevertheless, this is a great improvement for smaller deployments of Exchange Server 2010 where HA is still required.

Jaap Wesselius is the founder of DM Consultants, a company with a strong focus on messaging and collaboration solutions. After working at Microsoft for eight years, Wesselius decided to commit more of his time to the Exchange community in the Netherlands, resulting in an Exchange Server MVP award in 2007. He’s also a regular contributor at the Dutch Unified Communications User Group and a regular author for Simple-Talk.

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The Real Saina Nehwal has emerged

Former India badminton player Sanjay Sharma raises a toast to Saina after Denmark Open triumph

Saina Nehwal is only 22! But, she has broken enough records in Indian sport to be called a living legend. On a typical cold Sunday evening in Copenhagen, Saina cat-walked her way to yet another honour. She became the only Indian after Prakash Padukone (in 1980) to win a Danish Open Superseries title. And that too, without dropping a single game in the tournament.

Her 21-17, 21-8 victory in the final over Juliane Schenk of Germany was as emphatic as it was cruelly one-sided. An elated Pullela Gopichand, who has coached and nurtured Saina since she was 13, said after the final: “Saina was sharp, exceedingly efficient and explosive when it mattered. This was a drubbing and she was comfortable almost throughout, especially in the second game which was one-sided.”

Saina Nehwal poses with the Denmark Open Superseries trophy in
Copenhagen yesterday. Pic/AFP

This is her sixth Superseries title — a premier event in the sport — and like the Indonesian Open earlier in the year, this one too has cemented her place among the legends of world badminton. The Denmark Open was a huge field with three of the top-most Chinese stars competing.

The star-studded line-up included World No 1 and London Olympics silver medallist Wang Yihan, whom Saina had never beaten in their last six clashes. The heart-wrenching losses included a one-sided win for Wang in the semi-finals at London.

In Copenhagen though, Saina was in a different zone. The Hyderabadi hammered Wang 21-12, 12-7 in the semis before the lanky Chinese retired. The final frontier was thus conquered, and the fabled Chinese wall was demolished.

Saina has well and truly arrived! There is no one among the top players who she has not defeated. All the best names of her generation have now bitten the dust.

“It is all due to her work ethic. She is a glutton for hard work. She never says no for any sort of training schedule. And what is most mind-boggling for me, is that I can feel that her best is yet to come.

“Saina is just 22, still learning a few things. But what is important is that the more she wins, the more she wants to learn,” said Gopi.

I never expected to win here: Saina

Olympic bronze-medallist Saina Nehwal was not expecting to win the Denmark Open due to a slight niggle in her right knee. But she battled through the pain to triumph here and that to without dropping a set.

The 22-year-old defeated sixth seed German Juliane Schenk 21-17 21-8 in 35 minutes. Saina, who had beaten World No 1 Yihan Wang in the semi-finals, said: "I never expected to win this tournament. There were a lot of things which I did after Olympics which made me fresh but every tournament is tough. My right knee was not really in perfect shape but I thank god for giving me the energy to win the title.” 

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Asia's biggest Apple store opens in Beijing

Apple's largest store in Asia opened in Beijing Saturday.

The store, located in the city's commercial street of Wangfujing, is Apple Inc.'s third in Beijing, reported Xinhua.

John Browett, Apple's senior vice president of retail, had previously said that the new store is the company's largest store in Asia, with an area of 2,300 square meters and more than 300 employees.

A full range of accessories for Apple products is available in the store, according to Browett.

Hundreds of Apple fans waited in line before the store opened at 9 a.m.

"We will bite the 'Apple'," said one customer.

Apple currently has 390 retail stores around the world, and the company is stepping up its efforts to expand its presence in China.

Browett said a store in the south China city of Shenzhen is also about to open and there will be more stores across China in the future.

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Eight days with Microsoft Windows 8

(According to Microsoft,…)

Windows 8 is coming on October 26. But it is not just any other update to Windows, the most widely used operating system (OS) in the world. According to Microsoft, Windows 8 is re-imagining of the 25-years-old OS.

Windows 8 is publicly available as a Release Preview. I downloaded the 64-bit version, installed it onto a laptop and used it to see what sort of changes it brings for the end users. There are interesting and significant ways in which this Windows is different from its predecessors. All of them affect the way people use computers. Some in a good way and some in bad. Dive in to know how Windows 8 fared on my laptop...

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Facebook offering Rs. 50 talk time to new signups via mobile

Facebook India is currently running a promotion in the country, under which every new signup from social network's mobile website will get Rs. 50 talk-time. The social giant is also offering the same talk time if anyone signs up via your referral.

The promotion, which seems to have gone live around ten days ago, does not seem like a potent strategy and will only add to more fake profiles on the social network.

On one hand, the company seems to be worried about fake profiles and had recently reported the number to be as high as 83 million and on the other hand, it is launching offers which are likely to bring in more fake users rather than genuine ones.

New users will have to go to this link to signup and get the free talk time, which will be credited to their account in three days, notes Facebook on the signup page. The free talk time offer is not valid for existing users.

New users don't even need email address to register a new account, and will only need a mobile number that is not already associated with any other Facebook account.

Though details aren't available, Facebook would have likely tied up with a recharge service to provide the talk time to new users.

The social giant had recently crossed 1 billion monthly active users mark and is now focussing on developing countries like Brazil, India, and Mexico to get more users, as it struggles to get viable revenue sources in post-IPO era.

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Apple sends invite for 'iPad mini launch'

The invite, sent to reporters Tuesday, doesn't hint at what will be revealed, beyond saying that "We've got a little more to show you." The event will be held in San Jose, California.

NEW YORK: Apple has sent out invites for an event next Tuesday, where it's expected to announce the release of a smaller iPad. 

The invite, sent to reporters Tuesday, doesn't hint at what will be revealed, beyond saying that "We've got a little more to show you." The event will be held in San Jose, California. 

Media and analysts have said for months that Apple has an " iPad mini" in the works. The tablet is thought to be about half the size of the regular iPad and to start at $249 or $299. The regular iPad starts at $499 for the most recent models. 

Apple founder Steve Jobs derided the idea of a smaller tablet two years ago, but Amazon.comhas had some success with its Kindle Fire, which is about half the size of the iPad and starts at $159. Analysts believe Apple wants to tackle that competition with its own similarly sized tablet. 

Reports suggest that the smaller iPad would have a screen that's 7.8 inches on the diagonal, a bit more than the Kindle Fire or Google's Nexus, with their 7-inch screens. The full-size iPad has a 9.7-inch screen, giving it about twice the display area as the 7-inch units. 

Apple typically starts selling a new phone or iPad a week or two after announcing it. But it could treat the new iPad as a minor product update, in which case it could start selling it right after the announcement. 

Apple shares rose $14.02, or 2.2 per cent, to $648.78 in midday trading Tuesday. The shares are off their all-time high of $705.07, hit September 21 when the iPhone 5 went on sale in stores.

- Kirshna Kishore

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1 hour of watching TV shortens your life by 22 mins

Sitting on the couch and staring at the idiot box could be taking years off your life - 4.8 years to be exact, scientists have warned.

Australian researchers have found that for every hour of television viewed by a person over the age of 25, their life expectancy is reduced by 22 minutes, News.com.au reported.

The study was based on an average six hours viewing per day, compared to a person who watches no television.

Using data from the National Bureau of Statistics and the Australian Diabetes, Obesity and Lifestyle Study, the researchers generated life-expectancy tables based on the viewing habits of average Australians.

The results were alarming.

“TV viewing time may be associated with a loss of life that is comparable to other major chronic disease risk factors such as physical inactivity, smoking and obesity,” the study found.

“These findings suggest that substantial loss of life may be associated with prolonged TV viewing time among Australian adults.”

The research also revealed that in 2008, Australians aged 25 and older watched a total of 9.8 billion hours of TV that year alone.

Recent studies in the US also concluded that the average American spent 35.5 hours a week watching TV.

The study is the first of it’s kind to analyse the impact of television viewing on life expectancy, and has called for a public health case to warn adults of the risks of watching too much television.

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Apple’s iPad mini out on 23 Oct: Rumour round up

Apple is hosting an event on 23 October where it is widely expected that the 7-inch version of the iPad, already christened the ‘Mini’ by the media, is due to be launched. As always, the rumour mills are buzzing ahead of the launch. From price to versions of the iPad mini, here’s a look at what the tech sites are saying.

Price and Versions:

                  Mobile Geeks, already has a screengrab of the prices and the versions of the new device. According to their report, the device will have an 8 GB version, along with the regular, 16, 32 and 64 GB versions. Also it won’t be as cheap as the $199 Google Nexus or Amazon Kindle. The report states that the 8 GB version with just Wi-FI will be € 249 or a whopping $322.

TechCrunch has a detailed piece where they’ve broken down the cost of the iPad mini to reveal that it will be priced according to Apple’s profit margins.

The iPad mini is coming soon. AP

Big Orders: Is Apple expecting big sales for the iPad Mini? It would certainly seem so. According to the Wall Street Journal, component suppliers in Asia have say they have received orders to make more than 10 million units of the smaller tablets in the fourth quarter.

Design: According toAllThingsD, Apple will not sacrifice design aesthetics in the new iPad Mini. The report quotes analyst Brian White, who states that the Mini may even be slicker than the new iPad.

Battery: The battery size has also been leaked, if images on the tech site MacRumors are to be believed. According to this the iPad Mini will have a battery running at 3.72 volts, offering 16.7 Whr of energy on 4490 mAh of charge. This would put it the iPad mini’s battery in the range of Nexus 7 and Kindle Fire HD, which have a 16 watt-hour and 16.43 watt-hour unit, respectively.

Bonus launch

New MacBook Pro:According to 9to5Mac, Apple will also launch a a new 13-inch MacBook Pro with a Retina Display. This will be a thinner version of the 15-inch MacBook Pro with Retina Display that was launched in June.

The report also states that a new Mac Mini is on its way as well.

Overall it looks like Apple’s 23 October event will have a lot to offer.

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Apple poaches Samsung chip designer Jim Mergard: Report

Apple has reportedly swooped in to sign chip designer Jim Mergard from Samsung. The move comes in the backdrop of the bitterApple vs Samsung battle that has played out in courtrooms and markets all across the world.

Jim Mergard, a former AMD employee, joins Apple months after Jim Keller, a director in the platform architecture group and considered to be one of the key men behind Apple's A4 and A5 chips, left the company in August to make a return to AMD.

The Wall Street Journal was first to report Mergard's move:

The gadget maker (Apple) has hired Jim Mergard, a 16-year veteran of Advanced Micro Devices AMD who was a vice president and chief engineer there before he left for Samsung. He is known for playing a leading role in the development of a high-profile AMD chip that carried the code name Brazos and was designed for low-end portable computers.

The obvious thing for Mergard to do would be to join Apple's system-on-a-chip (SoC) design effort that has seen plenty of progress since the company first ventured in the territory with the Apple A4. More recently, the iPhone 5 is powered by Apple's A6 chip that is said to have twice as much CPU and GPU power compared to its predecessor.

WSJ also speculates if Mergard would design a custom-processor for use in Apple's Mac line. The report quotes Patrick Moorhead, a former AMD executive who now leads the research firm Moor Insights & Strategy, as saying that "He (Mergard) would be very capable of pulling together internal and external resources to do a PC processor for Apple."

While it's certainly possible for Apple to design a custom processor for use in its laptops and desktops, it's hard to see the company putting in a major effort towards that end considering Intel processors do a great job at the moment. More importantly, with a fundamental shift away from traditional computers already underway, and Apple at the forefront of that shift, any potential gains from having a custom chip in the Mac line, would be of minimum value at best.

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Gmail 4.2 app for Android leaks; shows pinch-to-zoom, swipe support

While core Android operating system might have had pinch-to-zoom support for a long time now, the official Gmail app has been lacking the same. But that seems set to change. A new version of Official Gmail Android app has appeared online and it shows pinch-to-zoom as well as swipe support.

According to a report in Android Police, Gmail Android app version number 4.2 is going to bring both these features to Android devices. This version will also allow users to mark mails as "phishing".

Similar to what Android users do in maps or browser, you can easily pinch-to-zoom in the mail text or image to view it clearly. The swipe support is also same as we have seen in notification bar; you can simple swipe an email message away to trash or archive now and if you accidentally do this, there is small undo button also present to save from any mishaps.

The swipe functionality will also be configurable, so you set it to archive, delete or just remove the existing label from an email.

There is no word on when we are going to see this app version rolled-out in Google Play. There is no official evidence either to support what Android Police is saying.

We will have to wait to see if Google really brings the pinch-to-zoom and swipe support to Gmail Android app.

watch video here..

http://www.youtube.com/watch?feature=player_embedded&v=00xUH86sJV0

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Samsung Galaxy S3 Mini hands on english

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Amazon's 'at-cost' Kindle Paperwhite and Fire HD near UK release

 The company's new tablets and e-readers are coming to Europe, along with Amazon's book-lending scheme, but Jeff Bezos says the firm is making no profit on the hardware. Instead, Amazon is relying entirely on its content strategy to make money off the devices.

Amazon's Kindle Fire HD tablet goes on sale in the UK on 25 October.

Amazon will also roll out its Lending Library in the countries for the first time, allowing Amazon Prime subscribers to borrow from a collection of 200,000 books for free.

The Paperwhite comes in Wi-Fi-only and Wi-Fi-plus-3G variants, priced at £109 and £169 respectively, while the seven-inch Kindle Fire HD tablet costs £169 for the 16GB version and £209 for the 32GB version. Customers get £10 off those Kindle Fire HD prices if they agree to see advertising on the device.

According to Amazon chief Jeff Bezos, the company is not making a profit on the devices themselves.

"We sell the hardware at our cost, so it's break-even on the hardware," Bezos told the BBC on Thursday. "We want to make money when people use our devices, not when they buy our devices. After you buy a Kindle Fire HD you may use it to buy books, games, movies and so on. So that continuing relationship with the customer is where we hope to make money over time."

Kindle comparisons

In the case of the Kindle Fire line, Amazon uses a forked version of Android that does away Google's Play Store and brings in Amazon's own storefront. With its e-readers, Amazon also makes it easy for customers to buy books at any time.

The Kindle Fire HD is a direct competitor to Google's Nexus 7 tablet, which is itself intended very much as a conduit to media sales. The similarly-priced devices both have a 1280 x 800-pixel resolution, although Amazon's tablet gives more storage for the price (the Nexus 7 comes in 8GB and 16GB versions), and Google's tablet is lighter (at 340g versus 396g) and more powerful (using a quad-core rather than dual-core processor).

The touch-controlled Kindle Paperwhite is a significant step up from earlier iterations of the device, as the screen comes with built-in illumination. Amazon is also making great play of the screen's high contrast and resolution, which is supposed to offer a more paper-like experience than the cheaper Kindles.

Then again, those entry-level, non-illuminated and non-touch Kindles are much cheaper, as they only cost £69.

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