VooServers
Reliable hardware  -  Trained Staff

Microsoft Exchange Server High Availability

Horizontal White Line


You are here:  Support / Technical Blog

Posted on  - By

History of Exchange HA

Prior to Exchange 2007, high availability and disaster recovery features were fairly limited and even up until Exchange 2010 these features relied heavily upon expensive technologies that were complex to implement. Exchange 2007 introduced Local Continuous Replication (LCR), Cluster Continuous Replication (CCR) and Standby Continuous Replication (SCR) although the latter came within Exchange 2007 SP1. LCR works pretty much as the name describes, a copy of the storage group is created on a second set of disks that are locally connected to the mailbox server. Now as you can tell this created a single point of failure at the hardware level, which is why CCR was much more popular as it utilized Windows Failover Clustering technology to provide redundancy at both the hardware and storage level. SCR then utilized the same technology as LCR and CCR to provide site resilience as it made it possible to ship the log files to another Exchange 2007 mailbox server. Exchange 2010 then dropped LCR and combined CCR and SCR to create Database Availability Groups (DAG).

Database Availability Groups

At the heart of Microsoft Exchange Servers High Availability and site resilience framework is Database Availability Groups. Introduced in Exchange 2010, enhanced in 2013 and still utilized in Exchange 2016, DAG’s are simply a group of up to 16 Mailbox servers, with each server hosting a set of databases. Once there is a failure of a DAG member, any active mailbox databases fail-over to another DAG member. The introduction of DAG removed several single points of failure, as there is no longer the reliance upon a single instance of a database – this is due to the ability to have up to 16 globally distributed database copies. This not only provides further resiliency but also reduces the need for technologies such as RAID or other traditional backups, if a hard drive was to fail numerous other database copies would already be available to activate. The progression of DAG has also made it incredibly simple to deploy and with the removal of the requirement for expensive high-performing storage solutions High Availability is now an affordable option in most installations.

New Additions to Exchange HA

Most of the High Availability enhancements within Exchange have been centred around improving the capabilities of the DAG including the introduction of lagged database copies. A lagged database copy is a copy of the database that isn’t updated by replaying transactions as they become available – instead the transaction logs are held for the defined period and then replayed. The primary reason is to provide access to a database that is at a certain point in time where it was known to be in a good state – therefore acting like an insurance policy should there be any form of corruption. If you were to be in the unfortunate situation where the active database had become corrupt then this would enable you to utilize the lagged database copy and bring the database back to a point prior to the corruption.

Replay Lag Manager

Replay Lag Manager was introduced in Exchange 2013, refined in 2016 and will be enabled by default in 2016 CU1. It enables Exchange to change a lag copy into a highly available copy if needed. Once Replay Lag Manager is enabled, it allows log replay to play down the log files in the following scenarios;

  • Low disk space threshold has been reached
  • Physical corruption to the lagged copy
  • When there are less than three available healthy highly available copies for more than 24 hours

Deferred Lagged Copy Play Down

This is an enhancement to the previously mentioned replay lag manager. If one of the above scenarios is triggered then a play down event will be initiated. The idea of deferred lagged copy play down is to assess the disks IO latency, if the disks read IO latency goes above 35ms then the play down event is deferred, once the disk’s ready IO latency drops below 25ms the play down event will be resumed. This is used to ensure the replaying of the transaction logs isn’t impacting the performance of any other databases on the same disk’s.

The graph below illustrates how this would work. As you can see between 1am and 9am the disk IO latency stays below 25ms and therefore lagged copy replay is allowed. Then at 10am the latecy rises above 35ms until 2pm so within this period lagged copy replay will be deffered. Once the latency then drops below 25ms at 2pm lagged copy replay will be resumed. This cycle will then continue any time the latency exceeds 35ms.

Disk Latency Overtime

Take for example the following scenario, you have a disk that holds four database copies– two active, one passive and one lagged. The above conditions are then met and a down play event is triggered. The resulting IO generated by the replaying log files has the potential to impact the active copies on that disk which would therefore impact any users accesing their data on the active copy. However with deferred lagged copy play down this is kept under control and will prevent any possible disruption during peak-hours. It’s important to note that the maximum amount of time that a play down event can be deferred is 24hours however this can be adjusted.





Posted on  - By

Emails are an essential part of day to day business and are relied upon heavily not only for communication but also for numerous other purposes such as marketing. It is due to this reliance that it is essential to be able to verify that your emails are being sent and received and this is exactly what email round-trip monitoring provides – a real world test that will confirm that your email communications are operating correctly.

Utilising email round-trip monitoring allows you to not only confirm your emails are being sent and received correctly but also to test and confirm other mechanisms that are vital to email deliverability, such as:

  • Confirming DNS MX records are correct
  • Mail server internet connectivity
  • Confirm email is flowing through spam and anti-virus filtering service correctly
  • Firewall configuration
  • Domain registration

How it Works

The basic idea behind ERT monitoring is for emails to pass through the specified mail server of which you’re testing and then back to the monitoring servers. This is achieved by sending emails from dedicated ERT monitoring servers at a specified interval (5,10,15,30 or 60 minutes) to a nominated test address. However, for this to be a true test of end to end deliverability, confirmation that the email was received, processed and delivered to the destination mailbox is required. Therefore, the mail server must acknowledge receipt of the test email by replying, this is commonly done by setting up automatic replies, forwarding or redirection of emails received from the monitoring servers. Once the monitoring servers have received a response, an analysis is performed which will provide details whether the email has had a successful round trip or whether there were any issues. If there are any failures and the monitoring servers haven’t received a reply back from the mail server then a notification is sent out.

At VooServers we utilise ERT monitoring to ensure reliable deliverability on all of our hosted email services, allowing our customers to have peace of mind knowing their emails are monitored 24/7. If you have any questions regarding ERT monitoring call us on 0800 0803 200





Posted on  - By

Microsoft have recently made available information detailing licensing changes for the upcoming release of Windows Server 2016. The main and most controversial change is the move from per-processor licensing to per-core licensing for both Windows Server 2016 Standard and Datacentre Editions. This will not only impact higher-core servers, but also the mandatory minimum of 16 cores, which is detailed further below, will greatly affect smaller servers.

According to the Licensing FAQ released by Microsoft, the main idea behind this change is to allow Microsoft’s server licensing to support the hybrid cloud and to make cores the common currency when licensing a Windows Server, with the intention to simplify licensing across multi-cloud environments. However unlike Microsoft’s SQL Server per-core licensing, Client Access Licenses (CAL’s) will still be required for both editions for every user or device accessing the server.

The way this works is that core licenses will be sold in packs of two licenses, each processor will need to be licensed with a minimum of 8 cores – 4 two-core packs. All physical cores within a server must be licensed and each physical server (including 1 processor servers) will need to be licensed with a minimum of 16 cores meaning the minimum required to license each physical server is 8 two-core packs. Then additional cores can be added in increments of 2 cores (1 two-core pack).

Microsoft’s licensing datasheet also notes that the price of 16-core licenses of Windows Server 2016 Standard and Datacentre edition will be the same price as the 2 proc license of the corresponding editions of Windows Server 2012 R2 version. To put this into perspective the two-core pack for each edition is 1/8th the price of a two proc licenses for the corresponding 2012 R2 edition.

As you can see from the image below, a server with up to 4 processors and up to 8 cores per processor will have the same overall licensing cost as 2012 R2. This can also be said for a system with a single 10 core processor, however a server with 2 or 4 processors and 10 or 20 cores will require additional licensing.

windows server 2016 licensing changes
*Microsoft

As Windows Server 2016 is licensed by physical cores and not virtual cores, hyper-threading does not affect the licensing as it is only necessary to license the physical cores on the processors. In addition to this, you do not have to license the cores on a processor that is disabled for use by Windows. Therefore, a 4 processor server with 8 cores per processor with 2 processors disabled and not available for Windows Server use, would only require 16 cores to be licensed.





Posted on  - By

If you’ve recently upgraded to Outlook 2016 you may have noticed attachments are handled a little differently. Referred to as “Modern Attachments”, this new and improved way of dealing with attachments adds extra functionality that not only makes it easier to share your files but also allows you to collaborate and set permissions. Also with the addition of cloud integration, within Outlook 2016 you will be able to utilise service such as OneDrive and SharePoint.

The first major change to Outlook 2016 is the addition of “Recent Items”. You’ll notice this straight away when attaching files. Instead of being presented with a prompt box to search for and insert your chosen file, you’ll see a list of the most recent files you’ve been working on. Obviously this is not a ground-breaking new feature but if you’d like to share a file with someone, the chances are that it’s one you’ve recently been working on. This intuitive feature removes the hassle of having to needlessly look through your files every time you want to attach a document, especially if it’s a file you’ve recently saved.

The standard way to attach files that everyone has become accustomed to within older versions of Outlook still exists – just tucked away under the “Browse This PC” option. However the main feature and probably the most beneficial addition to Outlook is the new “Browse Web Locations” option, utilising cloud storage, this allows you to “attach” files from OneDrive, OneDrive for Business and SharePoint. This not only opens up how you can share your files but also how you can control the permissions of any given file and limit what type of access you’d like the recipient to have– either View only or Edit permissions.

Outlook Browse web Locations


This may seem like a simple addition however the main benefit this feature provides is the fact that it allows you to send a link to any file you have stored on OneDrive, OneDrive for Business or SharePoint. This makes it much easier to maintain version control over your files – you will no longer have to repeatedly send the same document back and forth after every addition or change made to a file, therefore improving workflow and allowing you to efficiently collaborate with others. Not only does this feature make collaborating easier, it also prevents recipients from making unwanted changes to important documents.

Now as I’ve already stated, instead of attaching files to an email, cloud integration within Outlook 2016 works by allowing you to send a link to the file (stored on OneDrive or SharePoint) rather than attaching an actual copy of the file to the email. It is this feature that allows you to change and maintain control of the permissions on your files, therefore making version control so much easier – numerous people will be able to view or edit just one instance of the file as opposed to sending different re-iterations of the same file back and forth. This doesn’t mean that you can’t send actual copies of your files anymore, as there is also an option to “Attach as copy”, just in case someone needs a local copy of the file.

Overall the changes to attachments within Outlook 2016 provide users with more options when sharing their files, allowing them to not only have greater control but also improve workflow and efficiency.





Posted on  - By

Communication within any business is essential and at VooServers we rely on Skype for Business to help us communicate daily, from instant messaging a colleague to conferencing with a client in New York. Skype for Business is essentially a communication’s and collaboration platform packaged within an easy to use interface that boasts numerous features that makes day to day communication between colleagues and clients simple and effective.

Skype for Business Logo
Skype for Business (formerly known as Microsoft Lync) combines the features of Microsoft Lync with the user friendly interface and well known software Skype. This provides any business with the ability to provide Instant Messaging, voice and video calls, online meetings and much more all from within one software package. Furthermore as Skype for Business can be installed on most devices and even accessed via a web browser it gives almost every user with the ability to communicate across multiple devices and locations.

Instant Messaging

One of the main and often used features Skype for Business offers is the ability to send Instant Messages. This feature enables us to communicate instantly with another user in real time – be it a colleague or a client, regardless of their location as long as they have Skype for Business installed and an active network connection. However this is not the main benefit of instant messaging within Skype for Business as the software also allows users to share files, share their screen and there is even a presentation mode. All of these features are available within the conversation – which can be to one or multiple participants.

Screen Sharing & Presentation Mode One of the major benefits of Skype for Business is the ability to share your screen with other users by using the “Present” feature which is available within every conversation. As you can see from the below screenshot, not only can you share your desktop but also programs and PowerPoint presentation files. This allows for easy presentations to take place between colleagues, clients and even other companies. At VooServers we regularly use Instant Messaging, Screen Sharing and Presentation Mode to share resources or information between colleagues.

Skype for Business Interface
Below is a brief explanation of what each option does:

  • Present Desktop gives you the ability to share your entire screen as well as give control of your desktop to other participants within the conversation.
  • Present Programs allows you to choose a specific program to share or give control to other participants within the conversation. This is useful if you don’t want them to be able to see anything else on your computer other than the specified program.
  • Present PowerPoint Files allows you to choose a PowerPoint slide show to present to other participants within the conversation
  • More…

    • Whiteboard provides participants with access to a whiteboard, allowing you to collaborate or brainstorm, copy and paste notes and even save the whiteboard as a PNG file
    • Poll allows you to create a poll to gather feedback from participants
    • Q & A allows for answering of questions within a meeting in a structured format.
Voice & Video Calls

Other than instant messaging, Skype for Business also has the ability to start voice and video calls. This allows you to make and receive calls either from within your Contacts or to and from external numbers using devices such as headsets or IP Phones. This makes the use of Skype for Business cost effective to business’ as there’s no need for the installation and management of a landline. At VooSerevers we use the Voice Call feature daily to provide support to our clients. Not only does Skype for Business make this easy but it also gives us a simple interface to manage contacts of which we are in regular contact with.

Skype for Business Interface
Conference Calls

Another main feature within Skype for Business is the ability to create conference calls. This allows you to easily collaborate or present to other users whether they’re right next to you or in another country. This greatly benefits any business as it provides a simple way to hold a meeting with users in many different locations, as well as providing the ability for file sharing, screen sharing, whiteboard collaboration and presenting PowerPoint presentation slides. To add even more functionality, if Skype for Business is integrated with Microsoft Outlook you can schedule and join meetings from within the application itself.

Skype Federation

Federation or Skype for Business external connectivity enables a Skype for Business user to easily connect with any other user within other companies or organizations that use Skype for Business. Once connected the federated contacts are then able to communicate via Instant Messaging and Skype –to –Skype voice and video calls, as well as see the user’s presence (Available, Away, Offline). This makes communication between companies simple and easy. This is a feature we use often at VooServers as we are federated with numerous companies of which we provide support to. The main benefit of this is that it allows us to communicate with any users that are using Skype for Business within those companies. Another benefit of federation is that it enables you to access the consumer Skype directory and add those users to your contact list, effectively providing you with the ability to communicate with over 300 million users worldwide.

Integration with Office Applications

Skype for Business integrates easily with Microsoft Office. This enables you to see contact’s presences’, schedule meetings and start conversations all from within Office applications. This makes collaboration simple as numerous participants can see and simultaneously work on the same documents and eliminates the need to send documents back and forth for review and editing. Skype for Business also integrates with Outlook, providing features such as the ability to join or schedule meetings from within either Skype itself or Outlook and also integration with Outlook’s contact list. As Skype for Business can integrate with Exchange it has the ability to update a user’s presence based on the user’s Outlook calendar e.g. Skype for Business will access a user’s Outlook calendar, notice that the user is in a scheduled meeting and change the user’s presence, similar to the way it would if the user was in a voice or video call. This provides greater synchronisation between multiple applications and makes tasks between Outlook, Word and other Office applications seamless.

If you have any enquiries feel free to call 01622 524 200






© VooServers Ltd 2016 - All Rights Reserved
Company No. 05598165