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Four Free Training And Cloud Computing Resources

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Free Training And Cloud Computing Resources

Students with any interest in Information Technology or Computer Science are going to be joining a world dominated by Cloud Computing. Major cloud service providers (CSP) would love to see young people embrace their cloud platform to host the next big thing like Facebook, Instagram or SnapChat. The top three CSP offer Free Training And Cloud Computing Resources for students, hoping to win their minds and hearts.

But before you jump right in to cloud computing, the novice student might want to start with some basic fundamentals of computer programming at one of the many free Free Training And Cloud Computing Resources

Free Training And Cloud Computing Resources

Khan Academy is offering free Azure services for students. There are two different offerings. The first is targeted at high school students ages 13+ and the second is geared towards college students 18+.

Free Training And Cloud Computing Resources

Microsoft Azure for Students Starter Offer is for those high school students who are interested in building applications in the cloud. There are not many Free Training And Cloud Computing Resources being offered at the college level. But for the the self starter looking at dipping their toes in cutting edge technology, it’s a good place to start.

Azure for Students is targeted at the college level student and has many more features available for free. Any student in computer science or information technology should definitely try this. Perfect way to do it with no additional out of pocket expense.

A good way to get introduced to the Azure Cloud is to start with some free online training courses Microsoft delivers in partnership with Pluralsight.

Free Training And Cloud Computing Resources

Not to be outdone, AWS’ AWS Educate also offers some free cloud services to students and educators. It uses free cloud credits, which could go a long way if managed properly. AWS also delivers an educational program that can be combined with an AP class in Computer Science for interested educational institutions.

 

Free Training And Cloud Computing Resources

Google Cloud Platform (GCP) also has education grants available for computer science majors at accredited universities. These seem to be the most restrictive of the three as they are available for Computer Science Majors only at accredited universities.

Unfortunately, I do not seem to able to find the free training offered by GCP. If you want some hands on training you could register for some classes. The upside of this is that these classes all seem to be instructor led, either online or in an actual classroom. The downside is not many 13 year olds are going to shell out any money to start developing on the CGP when there are other free training opportunities available on AWS or Azure.

For more reading on Free Training And Cloud Computing Resources, visit here
Reproduced with permission from ClusteringForMereMortals.com

Fix Your SQL Server Multi-Subnet Failover Cluster

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Help! I Can’t Connect To My SQL Server Multi-Subnet Failover Cluster

Many of my customers have encountered this problem. To solve it, I usually tell them the following

The link would have everything you need to know.

They don’t go into great detail about what to do if your connection does not support multisubnetfailover=true. If your connection does NOT support that parameter, then set registerallprovidersip to false and cleanup DNS. That procedure is described best here.

How Does SQL Server Multi-Subnet Failover Cluster Actually Work?

In general people aren’t aware of how SQL Server Multi-Subnet Failover Cluster work. Multi-subnet failover clustering support was added in Windows Server 2012 with the addition of the “OR” technology when defining cluster resource dependencies. This allowed people to allow a Cluster Name resource to be dependent upon IP Address x.x.x.x OR IP Address y.y.y.y.
x.x.x.x would be an a cluster IP resource valid in Subnet A. y.y.y.y would be a cluster IP address valid in Subnet B. Only one address will be online at any given time, whichever address was valid for the subnet the resource was currently running on.
Microsoft SQL Server started supporting this concept starting with SQL Server 2012 with both failover cluster instances (FCI) using 3-party SANless clustering solutions like SIOS DataKeeper and SQL Server Always On Availability Groups.
By default if you create a SQL Server Multi-Subnet Failover Cluster, the cluster should be automatically configured optimally. This includes setting up the two IP addresses, adding two A records to DNS and setting the registerallprovidersIP to true. However, on the client end you need to tell it that you are connecting to a multi-subnet failover cluster, otherwise the connection won’t be made.

Configuring The Client

Configuring the client is done by adding multisubnetfailover=true to the connection string. This Microsoft documentation is a great resource. But if you just search for multisubnetfailover=true you will find a lot of information about that setting.
Do not that not every application will support adding that to the connection string. If you find yourself in that situation you should ask your application vendor to add support for that or show you how to do it.
Fret not. All is not lost if you find yourself in that situation. You will want to change the behavior of the cluster so that upon failover DNS is update so that the single A record associated with the cluster client access point is updated with the new IP address. This is in lieu of having two A records in DNS, one with each cluster IP address, which is the default behavior in an multi-subnet cluster.

Help Is On The Way

This article reference SharePoint, you can ignore that, the rest of the article is pretty well written to describe the process you should follow.
The highlights of that article are as follows…
Get-ClusterResource “[Network Name]” | Set-ClusterParameter RegisterAllProvidersIP 0
After restarting the cluster-name-object (basically restarting the role) & cleaning up all “A” records manually (clean-up isn’t done automatically) we can see our old A-records are still in DNS so we’ll need to delete those manually.
In addition to those steps I’d advise you to reduce the TTL on the HostRecordTTL as described in this article.
The highlight of that article is as follows.
PS C:\> Get-ClusterResource -Name cluster1FS | Set-ClusterParameter -Name HostRecordTTL -Value 300
With a Value of 300 you could potentially be waiting up to 5 minutes for your clients to reconnect after a failover, or even longer if if have a large Active Directory infrastructure and AD replication takes some time to update all the DNS servers across your infrastructure.
You are going to want to figure out what the optimal TTL is to facilitate quick client reconnections without over burdening your DNS servers with a bunch of DNS Lookup requests.
This type of configuration is common in disaster recovery configurations where your DR site is in a different subnet. It is also very common in HA deployments in AWS because different Availability Zones are in different subnets.
Let me know if you have any questions about SQL Server Multi-Subnet Failover Cluster. You can always reach me on Twitter @daveberm

Can I Put My File Share Witness On A DFS Share?

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Can I Put My File Share Witness On A DFS Share?

Can I Put My File Share Witness On A DFS Share?

I get asked this question all the time – Just where can put my File Share Witness On A DFS Share. People are concerned about losing their file share witness. Hence like many of their other shares, they want to leverage DFS for some additional availability. This is a very bad idea and is not supported.

Microsoft recently publish a great blog article that describes exactly why File Share Witness On A DFS Share is not supported.

https://blogs.msdn.microsoft.com/clustering/2018/04/13/failover-cluster-file-share-witness-and-dfs/

Much of this article would also apply to people who ask if they can use a DataKeeper replicated volume resource as a Disk Share. It makes sense. You can use a DataKeeper volume resource in place of a Physical Disk resource for any other workload, so why not a Disk Witness?

This issue is the same as the DFS issue. In the event of a loss of communication between the two servers, there is nothing to guarantee that the volume wouldn’t come online on both servers. It would result in a potential split-brain condition. The Physical Disk resource overcomes this issue by using SCSI reservations. This would ensure the disk is only accessible by one cluster node at a time.

The good news is that Microsoft already blocks you from trying to use a replicated DataKeeper Volume resource. And coming in Windows Server 2019, it looks like they will also block you from using a DFS share as a File Share Witness.

Can I Put My File Share Witness On A DFS Share?
Taken from the Failover Clustering and Network Load Balancing Team Blog Post “Failover Cluster File Share Witness and DFS

Have questions like this about putting File Share Witness On A DFS Share? Read through our blog or contact us!
Reproduced with permission from ClusteringForMereMortals.com

Network Speed Between Azure Regions Connected With Virtual Network Peering

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What Is The Network Speed Between Azure Regions Connected With Virtual Network Peering?

This is the question I asked myself today. Of course I couldn’t find the reason behind Network Speed Between Azure Regions Connected With Virtual Network Peering documented anywhere. I’m assuming there is no guarantee. It probably depends on current utilization, etc. If I’m wrong, someone please point me to the documentation that states the available speed. I primarily looked here and here.

So I set up two Windows 2016 D4s v3 instances – one in Central US and one in East US 2. Both are paired regions.

If you don’t know what peering is, it essentially lets you to easily connect two different Azure virtual networks. Peering is very easy to setup. Just make sure you configure it from both Virtual Networks. Once it is configured properly it will look something like this.

Doing Tests

What Is The Network Speed Between Azure Regions Connected With Virtual Network Peering?
A properly functioning peered network in Azure

I then downloaded iPerf3 on each of the servers and began my testing. At first I had some pretty disappointing results.

But then upon doing some research, I found that running multiple threads and increasing the window size reports a more accurate measurement of the available bandwidth. I tried a few different setting. It seemed to max at at just about 1.9 Gbps on average, much better than 45 Mbps!

I used the client parameters and produced the best results. See as follows:

iperf3.exe -c 10.0.3.4 -w32M -P 4 -t 30

A sample of that output looks something like this.

- - - - - - - - - - - - - - - - - - - - - - - - -
 [ 4] 2.00-3.00 sec 34.1 MBytes 286 Mbits/sec
 [ 6] 2.00-3.00 sec 39.2 MBytes 329 Mbits/sec
 [ 8] 2.00-3.00 sec 56.1 MBytes 471 Mbits/sec
 [ 10] 2.00-3.00 sec 73.2 MBytes 615 Mbits/sec
 [SUM] 2.00-3.00 sec 203 MBytes 1.70 Gbits/sec
 - - - - - - - - - - - - - - - - - - - - - - - - -
 [ 4] 3.00-4.00 sec 37.5 MBytes 315 Mbits/sec
 [ 6] 3.00-4.00 sec 19.9 MBytes 167 Mbits/sec
 [ 8] 3.00-4.00 sec 97.0 MBytes 814 Mbits/sec
 [ 10] 3.00-4.00 sec 96.8 MBytes 812 Mbits/sec
 [SUM] 3.00-4.00 sec 251 MBytes 2.11 Gbits/sec
 - - - - - - - - - - - - - - - - - - - - - - - - -
 [ 4] 4.00-5.00 sec 34.6 MBytes 290 Mbits/sec
 [ 6] 4.00-5.00 sec 24.6 MBytes 207 Mbits/sec
 [ 8] 4.00-5.00 sec 70.1 MBytes 588 Mbits/sec
 [ 10] 4.00-5.00 sec 97.8 MBytes 820 Mbits/sec
 [SUM] 4.00-5.00 sec 227 MBytes 1.91 Gbits/sec
 - - - - - - - - - - - - - - - - - - - - - - - - -
 [ 4] 5.00-6.00 sec 34.5 MBytes 289 Mbits/sec
 [ 6] 5.00-6.00 sec 31.9 MBytes 267 Mbits/sec
 [ 8] 5.00-6.00 sec 73.9 MBytes 620 Mbits/sec
 [ 10] 5.00-6.00 sec 86.4 MBytes 724 Mbits/sec
 [SUM] 5.00-6.00 sec 227 MBytes 1.90 Gbits/sec
 - - - - - - - - - - - - - - - - - - - - - - - - -
 [ 4] 6.00-7.00 sec 35.4 MBytes 297 Mbits/sec
 [ 6] 6.00-7.00 sec 32.1 MBytes 269 Mbits/sec
 [ 8] 6.00-7.00 sec 80.9 MBytes 678 Mbits/sec
 [ 10] 6.00-7.00 sec 78.5 MBytes 658 Mbits/sec
 [SUM] 6.00-7.00 sec 227 MBytes 1.90 Gbits/sec

I saw spikes as high as 2.5 Gbps and lows as low as 1.3 Gbps.

Update From Twitter

So I received some feedback from @jvallery that I must try out.

What Is The Network Speed Between Azure Regions Connected With Virtual Network Peering?

First thing I did was bump up my existing instances to D64sv3 and used -P 64. I saw a significant increase

iperf3.exe -c 10.0.3.4 -w32M -P 64 -t 30

[SUM] 0.00-1.00 sec 2.55 GBytes 21.8 Gbits/sec

I then spun up some F72v2 instances as suggested and I saw even better results.

iperf3.exe -c 10.0.2.5 -w32M -P 72 -t 30

[SUM] 0.00-1.00 sec 2.86 GBytes 24.5 Gbits/sec

 

I’m not well versed enough in Linux. Bu there seems to be a reasonable amount of bandwidth available between Azure regions when using peered networks.

If someone wanted to repeat this test using Linux as @jvallery suggested, I’ll be glad to post your results here! Seems that there is indeed to possible to vary the Network Speed Between Azure Regions Connected With Virtual Network Peering.

Using SIOS DataKeeper For Disaster Recovery

For one of my clients, I chose to use these two peered networks to address SQL Server disaster recovery using SIOS DataKeeper to asynchronously replicate SQL data between regions for disaster recovery.

What Is The Network Speed Between Azure Regions Connected With Virtual Network Peering?
SIOS DataKeeper replicating data from Azure EAST US 2 to CENTRAL US

In this particular scenario, we were measuring a RPO measured in milliseconds. As you’ll see in the video below, during a DISKSPD test meant to simulate a typical SQL Server workload the RPO was <1 second.

I’d love to hear from you regarding your experience regarding any network speed you measure in Azure and how you are using peered networks in Azure.

Have questions about Network Speed Between Azure Regions Connected With Virtual Network Peering? Read through our blog or contact us!
Reproduced with permission from ClusteringForMereMortals.com

Convert Azure Clusters To Managed Disks

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Why you should convert azure clusters to managed disks

Why You Should Convert Azure Clusters To Managed Disks

You may have heard about the recent storage outage that impacted some instances in the US East region back on March 16th. A root cause analysis of the outage is posted here. March 16th US East Storage Outage

Customer Impact

A subset of customers using Storage in the East US region may have experienced errors and timeouts while accessing their storage account in a single Storage scale unit.

You might be asking, “What is a single Storage scale unit”. Well, you can think of it as a single storage cluster, or single SAN, or however you want to think about it. I don’t think Azure publishes their exact infrastructure. Although you can probably assume that behind the scenes they are using Scale Out File Servers for backend storage.

Survive The Outage With Minimal Downtime

So the question is, how could I have survived this outage with minimal downtime? If you read further down that root cause analysis you come across this little nugget.

Virtual Machines using Managed Disks in an Availability Set would have maintained availability during this incident.

Hence, it is time to Convert Azure Clusters To Managed Disks

What’s Managed Disks?

On February 8th Corey Sanders announced the GA of Managed Disks.

Managed Disks would have helped in this outage. Because by leveraging an Availability Set combined with Managed Disks, each of the instances in your Availability Set are connected to a different “Storage scale unit”. So in this particular case, only one of the cluster nodes would have failed, leaving the remaining nodes to take over the workload.

Prior to Managed Disks being available (anything deployed before 2/8/2016), there was no way to ensure that the storage attached to your servers resided on different Storage scale units. Sure, you could use different storage accounts for each instances. But in reality that did not guarantee that those Storage Accounts provisioned storage on different Storage scale units. More reasons to Convert Azure Clusters To Managed Disks.

So while an Availability Set ensured that your instances reside in different Fault Domains and Update Domains to ensure the availability of the instance itself, the additional storage attached to each instance really represented a single point of failure. Although the storage itself is highly resilient, with three copies of your data and geo-redundant options available, in this case with a power failure the entire Storage scale unit went down along with all the servers attached to it.

So long story short… Convert Azure Clusters To Managed Disks as soon as possible in order to help minimize downtime

https://docs.microsoft.com/en-us/azure/virtual-machines/virtual-machines-windows-migrate-to-managed-disks

And if you really want to minimize downtime you should consider Hybrid Cloud Deployments that span cloud providers or on-prem to cloud!

Reproduced with permission from Clusteringformeremortals.com