Yellow Bricks

by Duncan Epping

ESX

HA Cli

· ·

I was just playing around with the HA Cli and noticed that when you give an “ln” (listNodes) that the failover coordinator (aka master primary) is also listed. I have never noticed this before, but don’t have a pre-vSphere 4.1 environment to test it on to see if this existed before 4.1. If you want to test it in your own environment just simply run “/opt/vmware/aam/bin/Cli” and give the “ln” command as shown in the screenshot below:

I also tested demoting of a node just for fun. In this case I demoted the node “esxi1” from primary to secondary:

And of course I promoted it again to primary:

 

** Disclaimer: This article contains references to the words master and/or slave. I recognize these as exclusionary words. The words are used in this article for consistency because it’s currently the words that appear in the software, in the UI, and in the log files. When the software is updated to remove the words, this article will be updated to be in alignment. **

VMware related acronyms

· ·

We were just talking about some random VMware acronyms during a lab day and I thought I would write the ones down which some of us didn’t know. (Even google did not have the answer to some) I guess the most difficult one to figure out was VPXA/VPXD, which refers to VPX which was the official name for vCenter back in the days….

  • FDM = Fault Domain Manager
  • CSI = Clustering Services Infrastructure
  • PAE = Propero Application Environment
  • ESX = Elastic Sky X
  • GSX = Ground Storm X or Ground Swell X
  • VPX = Virtual Provisioning X
  • VPXA = Virtual Provisioning X Agent
  • VPXD = Virtual Provisioning X Daemon
  • VMX = Virtual Machine eXecutable
  • AAM = Automated Availability Manager
  • VIX = Virtual Infrastructure eXtension
  • VIM = Virtual Infrastructure Management
  • DAS = Distributed Availability Service
  • ccagent = Control Center agent
  • vswif = Virtual Switch Interface
  • vami =Virtual Appliance Management Infrastructure
  • vob = VMkernel Observation
  • MARVIN = Modular Automated Rackable Infrastructure Node
  • WCP = Workload Control Plane

How about code names for releases? Well we had a couple, note that the first name usually refers to ESX and the second to vCenter, so for KL “Kadinsky” was the code name for ESX and Logan for vCenter:

  • DM = Dali/McKinley = VI 3.0
  • NP = Neptune/Pluto = VI 3.5
  • KL = Kadinsky/Logan = vSphere 4.0
  • KL.next = vSphere 4.1
  • MN = Matisse/Newberry = vSphere 5.0
  • OP = Oliveira/Pikes = vSphere 5.5

Of course the big question is where the “X” comes from in ESX, GSX etc. To be honest I don’t know but according to VMware old-timer Mike Di Petrillo (source is this interview (21:30) by Rodney Haywood) the X had been added by an Engineer to make it sound technical and cool!

If there are any to VMware related acronyms that you feel should be on the list which are not too obvious… leave me a comment. (And too obvious would be something like vDS.)

Storage Migrations?

· ·

On an internal mailing list we had a very useful discussion around storage migrations when a SAN is replaced or a migration needs to take place to a different set of disks. Many customers face this at some point. The question usually is what is the best approach? SAN Replication or Storage vMotion… Both have its pros and cons I guess.

SAN Replication:

  • Can utilize Array based copy mechanisms for fast replication (+)
  • Per LUN migration, high level of concurrency (+)
  • Old volumes still available (+)
  • Need to resignature or mount the volume again (-)
    • A resignature also means you will need to reregister the VM! (-)
  • Downtime for the VM during the cut over (-)

Storage vMotion:

  • No downtime for your VMs (+)
  • Fast Storage vMotion when your Array supports VAAI (+)
    • If your Array doesn’t support VAAI migrations can be slow (-)
    • Induced cost if VAAI isn’t supported (-)
    • Only intra Array not across arrays (-)
  • No resignaturing or re-registering needed (+)
  • Per VM migration (-)
    • Limited concurrency (2 per host, 8 per vmfs volume) (-)

As you can see both have its pros and cons and it boils down to the following questions:

How much down time can you afford?
How much time do you have for the migration?

HA/DRS and Flattened Shares

· ·

A week ago I already touched on this topic but I wanted to get a better understand for myself what could go wrong in these situations and how vSphere 4.1 solves this issue.

Pre-vSphere 4.1 an issue could arise when shares had been set custom on a virtual machine. When HA fails over a virtual machine it will power-on the virtual machine in the Root Resource Pool. However, the virtual machine’s shares were scaled for its appropriate place in the resource pool hierarchy, not for the Root Resource Pool. This could cause the virtual machine to receive either too many or too few resources relative to its entitlement.

A scenario where and when this can occur would be the following:

VM1 has a 1000 shares and Resource Pool A has 2000 shares. However Resource Pool A has 2 VMs and both will have 50% of those “2000” shares.

When the host would fail both VM2 and VM3 will end up on the same level as VM1. However as a custom shares value of 10000 was specified on both VM2 and VM3 they will completely blow away VM1 in times of contention. This is depicted in the following diagram:

This situation would persist until the next invocation of DRS would re-parent the virtual machine to it’s original Resource Pool. To address this issue as of vSphere 4.1 DRS will flatten the virtual machine’s shares and limits before fail-over. This flattening process ensures that the VM will get the resources it would have received if it would have been failed over to the correct Resource Pool. This scenario is depicted in the following diagram. Note that both VM2 and VM3 are placed under the Root Resource Pool with a shares value of 1000.

Of course when DRS is invoked  both VM2 and VM3 will be re-parented under Resource Pool A and will receive the amount of shares they had originally assigned again. I hope this makes it a bit more clear what this “flattened shares” mechanism actually does.

Workaround for: ESX(i) 4.1 Password Issue

· ·

As many of you already know there is an issue with the encryption mechanism of ESX(i) 4.1. When passwords are used which are longer than 8 characters the password will be truncated after the 8th character. As such during authentication only the first 8 characters are used. In other words if you have  a 10 character password you will only need to type the first 8 characters correct and the rest can be completely random.

The KB article that was published yesterday contains a workaround to change this behaviour. I recommend everyone to read the article and implement this workaround when your password policy describes passwords longer than 8 characters.