clustering

Database clustering support for vCloud Director added in version 5.1!

Duncan Epping · Oct 18, 2012 ·

Those who have been architecting vCloud Director environments from the early days know that this has always been a pain point. I personally have had many discussions with product management and engineering to get support for database clustering like Oracle RAC or Microsoft clustering services for MS SQL. Unfortunately neither 1.0 and 1.5 supported it. So the big questions always was, when will database clustering support for vCloud Director be added?

I had a couple of discussions around this again last week and noticed it was still not listed until someone pointed me to the vCAT 3.0 documents. Hidden on page 110 of document “3a Architecting a VMware vCloud.pdf” I found the following statement:

VMware vCloud component database resiliency is provided through database clustering. Microsoft Cluster Service for SQL and Oracle RAC are supported.

Yes I do realize that this is not a KB article, or even mentioned in the vCloud Director documentation. I have requested the docs to be revised and a KB to be created. Hopefully those will follow soon, for now this statement is all we needed! When the docs are revised or a KB is published I will add the references to this article.

<update – 18/Oct/2012> KB just got added – http://kb.vmware.com/kb/2037802 </update>

Can I get your book for free?

Duncan Epping · Oct 11, 2012 ·

Well not from me, but CloudPhysics has a nice book give-away going on at the moment for the VMworld Barcelona attendees! So what do you need to do?

How To Win

Email us at [email protected] with a subject of “Book”. No message is needed.

Register at http://www.cloudphysics.com/ by clicking “SIGN UP”.

Install the CloudPhysics Observer vApp to activate your dashboard.

Eligibility

You are attending VMworld Barcelona.

You are a new CloudPhysics user.

You fully install the CloudPhysics ‘Observer’ vApp in your vSphere environment.

That is an easy way of getting the book for free right? So I suggest you head over and sign up to make sure you are part of the first 150 users that gets a free book!

Out on iBooks finally – vSphere 5.1 Clustering Deepdive

Duncan Epping · Oct 1, 2012 ·

It took about about a month to get this published, but here it finally is: vSphere 5.1 Clustering Deepdive on iBooks.

Yeah yeah, we know… you also want Nook and lulu.com says it is pending so that means it probably takes a couple of days before it is up on Barnes and Nobles as well.

Why is my pathing policy limited to “fixed” or “MRU” with things like MSCS cluster?

Duncan Epping · May 17, 2012 ·

Yesterday I received an email from someone. He wanted to know why he was limited to using either the “fixed” or “MRU” pathing policy for the LUNs attached to his MSCS cluster. In his environment they used round-robin for everything and not being able to configure all of them with the same policy was against their internal policy. The thing is that if round-robin would be used and the path would switch (by default every 1000 I/Os) the SCSI-2 reservation would need to be re-acquired on this LUN. (MSCS uses SCSI-2 reservations for their cluster devices) As you can imagine that could cause a lot of stress on your array and could lead to all sorts of problems. So please do not ignore this recommendation! Some extra details can be found in the following KB articles:

What is das.maskCleanShutdownEnabled about?

Duncan Epping · Apr 25, 2012 ·

I had a question today around what the vSphere HA option advanced setting das.maskCleanShutdownEnabled is about. I described why it was introduced for Stretched Clusters but will give a short summary here:

Two advanced settings have been introduced in vSphere 5.0 Update 1 to enable HA to fail-over virtual machines which are located on datastores which are in a Permanent Device Loss state. This is very specific to stretchec cluster environments. The first setting is configured on a host level and is “disk.terminateVMOnPDLDefault”. This setting can be configured in /etc/vmware/settings and should be set to “True”. This setting ensures that a virtual machine is killed when the datastore it resides on is in a PDL state.

The second setting is a vSphere HA advanced setting called “das.maskCleanShutdownEnabled“. This setting is also not enabled by default and it will need to be set to “True”. This settings allows HA to trigger a restart response for a virtual machine which has been killed automatically due to a PDL condition. This setting allows HA to differentiate between a virtual machine which was killed due to the PDL state or a virtual machine which has been powered off by an administrator.

But why is “das.maskCleanShutdownEnabled” needed for HA? From a vSphere HA perspective there are two different types of “operations”. The first is a user initiated power-off (clean) and the other is a kill. When a virtual machine is powered off by a user, part of the process is setting the property “runtime.cleanPowerOff” to true.

Remember that when “disk.terminateVMOnPDLDefault” is configured your VMs will be killed when they issue I/O. This is where the problem arises, in a PDL scenario it is impossible to set “runtime.cleanPowerOff” as the datastore, and as such the vmx, is unreachable. As the property defaults to “true” vSphere HA will assume the VMs were cleanly powered off. This would result in vSphere HA not taking any action in a PDL scenario. By setting “das.maskCleanShutdownEnabled” to true, a scenario where all VMs are killed but never restarted can be avoided as you are telling vSphere HA to assume that all VMs are not shutdown in a cleanly matter. In that case vSphere HA will assume VMs are killed UNLESS the property is set.

If you have a stretched cluster environment, make sure to configure these settings accordingly!