24. February 2013 22:23
In SQL Server 2012, we have 4 main options for High Availability: Database Mirroring, Failover Clustering, Availability Groups and Log Shipping. All but Availability Groups (AG) are available in SQL Server 2008 as well. Today we’ll review Availability Groups and how to create and use them.
Before we begin, make sure you understand what is Windows Server Failover Cluster (WSFC). I covered it almost a year ago for Windows Server 2008 R2 and SQL Server 2008 R2, and you’ll need WSFC in order for AG to work.
A few points about Availability Groups to make sure they are what you are looking for:
- Availability Groups are not share-nothing scalability option. They are using shared storage, such as storage area network (SAN), although it’s not a requirement. We’ll speak about share-nothing scalability later.
- For AlwaysOn Availability Groups, you need SQL Server 2012 Enterprise edition or higher. Business Intelligence edition or Standard won’t do.
- AG provide failover with up to 5 readable nodes.
- AG provide you with something like load balancing option, but AG is not NLB. Also, all nodes can work independently, i.e. you can still connect to them to retrieve information. Only the primary node can change information in the database.
- AG does not require working in the same IP subnet, but it requires Active Directory domain. This means, that you can have geographically remote nodes participating in one AG, but they must be members of the same AD domain.
In case of multi-subnet cluster, you’ll have to implement the file replication solution on your file servers to synchronize the data.
- AG is database-level, as opposed to node-level failover cluster. AG serves group of databases, unlike the simple database mirroring, with 4 replicas instead of one.
Overall, the AlwaysOn Availability Groups are conceptually similar to database mirroring, but provide more advanced functionality and security.
16. February 2013 07:00
If you are developer, then you work with relational databases as well. And if you work in a Windows world, most likely your system of choice is Microsoft SQL Server.
With every new DBMS release we find something that changes the way we solve common problems in new solutions. SQL Server 2012 is no exception.
In SQL Server 2012, instead of just enhancing the productivity and robustness of the server, Microsoft solved a number of architectural problems we previously had to deal with in our applications when working with SQL Server.
Problems like saving files in databases, load balancing database clusters and simple restoration of data, finally got the minimum viable solution, which should only improve with time. More...
6. October 2012 22:22
This article is about free software I made to automate the deployment of exported Hyper-V machines. More precisely – Hyper-V machines of labs for Microsoft Official Curriculums (MOC), used by students at Microsoft official training classes. It should be interesting for MCTs (i.e. Microsoft Certified Trainers) out there, whose job is to deploy labs in form of Hyper-V virtual machines, as well as for system administrators having the same duty of periodic installation of Hyper-V virtual machines. The installation procedure of a pack of Hyper-V machines could be extremely time consuming. Or should I say - used to be.
I will speak about it as about the solution for a lab deployment problem, but if you are working with other virtual machines, just think about the similarities with your scenario.
27. September 2012 14:32
Well, the “unexpected” should be put into quotes, because if you went through the Windows 8 training, then you have some ideas about how it works, but even if you did the training, some things are not clear until you crash at them at full speed.
As I mentioned before, Windows 8 now suspends applications which loose their focus. In Metro applications framework you, as developer, can deal with suspension notice and make sure you save the current state of the application, and you could use application manifest to create exception from the rule. Say, if your application is a media player or a browser.
However, it turns out that Metro applications are not the only ones to be suspended. More...
27. August 2012 13:37
Sometimes I need to copy large files simultaneously to several tens of computers. Like – Hyper-V virtual machines for training courses, and sometimes they take up to 60 Gigabytes. Usually these files reside on a single file server, connected to the local network by 1Gbit NIC, but even if nothing else is taking the bandwidth from that file server, copying 60 Gb to 20 machines would take more than 11 hours – that’s the amount of time it takes to transfer 1200 Gb at the speed of 30 Megabytes per second.
I wanted to reduce the overall time of deployment to about 70-90 minutes, or about 10 times. And this article is about how I’ve accomplished that goal.
20. April 2012 14:41
A few days ago Microsoft released beta of their new technology called User Experience Virtualization, or UE-V. The name implies that it has something to do with virtualization, but it’s just a buzzword. What UE-V does – it synchronizes user settings across workstations, in real time.
Imagine, that you have to log into multiple workstations, and what you want to have is the same settings of all applications you are using in your work. For example, spelling options in Microsoft Office, the layout of buttons, menus and colors – all the little pains that accumulates into the strong headache of roaming for some.
UE-V vs. roaming profiles
The roaming profile could be the answer, but for most of us it’s not. Some of us don’t even have the Active Directory profiles, but still desire the same user experience throughout the environment (translation to human language: every desktop of yours looks and behaves the same).
The difference with roaming is also in fact that in UE-V you only synchronize what you want to, not everything. So it works faster and has less space for errors.
19. April 2012 17:45
With a catch. The topmost certification for windows system administrators, the MCSE (Microsoft Certified Systems Engineer) got new name, while keeping the old abbreviation. Now it’s called Microsoft Certified Solutions Expert.
No. Sorry. In fact, Microsoft created brand new certification, mixed products with the cloud and gave it the acronym of the most successful Microsoft’s certification, coincidentally abandoned since 2003. More...
19. April 2012 06:45
About 5 months ago, I made a video about configuring the network load balancing cluster in Windows Server 2008. I am continuing the series about clustering the Windows Server 2008 with the next type of clusters – the failover cluster. Also known as “high availability” cluster.
Although Windows Server 2008 supports 4 types of clusters – Network Load Balancing, Failover, Computational and Grid, the most commonly used are the first two. Also, we’ll talk about the private clouds later, as they are doing similar job, but in Windows Server 2008 the private cloud is the functionality of an application called System Center Virtual Machine Manager 2012, so it’s not the system core feature, such as clustering.
During the series of demos we’ll talk mainly about failover and network load balancing clusters, as the High Performance Computational cluster requires it’s own special edition of Windows Server 2008, called Windows Server 2008 R2 HPC Edition, and chances are – you won’t ever have the requirement to set up such environment.
Windows Server 2008 Cluster Categories
As you can see in the following slide, there are two categories of clusters by the way they share resources.
Failover cluster belongs to the second group, which means that it is a group of computers, where only one node (i.e. the machine participating in the cluster) owns the resource. You may have two or more machines working as nodes in your failover cluster, but only one of them will serve clients at any moment of time. Once that machine fails, another node takes ownership of resources (shared drive, for example) and starts serving clients instead of the failed node.
31. March 2012 05:37
The problems of Search Engine Optimization are usually considered to be the problems of the marketing division of the company, and system administrators or software developers almost always have no clue when what they do causes significant troubles for website marketing.
Today we will talk about one of the biggest problems you may encounter in Search Engine Optimization – the content duplication problem, and what you, as web developer, system administrator or website owner, should do to prevent it.
30. March 2012 17:58
In this short video, which is rather addition to the 4th part of the PowerShell introduction videos for Windows system administrators, I am showing the basic concepts of script flow control.
This is very natural and basic for software developers, but system administrators with no prior experience in Windows PowerShell may find it very useful.
In this particular example we are connecting to the remote computer and listing it’s network adapters, to do different things depending from whether these adapters are DHCP enabled or not.