Yellow Bricks

by Duncan Epping

Archives for 2009

SRM 4.0 Evaluator Guide

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For those starting out with SRM 4.0 the following documents/links might be very useful:

  • Site Recovery Manager 4.0 Evaluator’s Guide
    The Site Recovery Manager 4.0 Evaluator’s Guide is intended to provide Site Recovery Manager customers and evaluators a guide that walks them through the Site Recovery Manager workflow that has to be completed to allow for the successful and automated service failover from the designated Site Recovery Manager protected site to the designated Site Recovery Manager recovery site. It also provides an overview that includes the considerations and guidance to execute a failback of services from the recovery site back to the site that was originally designated as the Site Recovery Manager protected site. In addition, this guide covers the new Site Recovery Manager features – VMware vSphere support, NFS support, and shared recovery site. Evaluators can work through the exercises provided in this guide to gain a first-hand experience on operating the core and new features.
  • A Quick tour of SRM 4.0
    Now that SRM 4.0 is here it seemed like a good time to take quick tour around a few of the new features and also highlight some less obvious elements of the vSphere platform that make working with SRM 4.0 simpler

Slot sizes

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I’ve been receiving a lot of questions around slot sizes lately. Although I point everyone to my HA Deepdive post not everyone seems to understand what I am trying to explain. The foremost reason is that most people need to be able to visualize it; which is tough with slot sizes. Just to freshen up an outtake from the article:

HA uses the highest CPU reservation of any given VM and the highest memory reservation of any given VM. If there is no reservation a default of 256Mhz will be used for the CPU slot and the memory overhead will be used for the memory slot!

If VM1 has 2GHZ and 1024GB reserved and VM2 has 1GHZ and 2048GB reserved the slot size for memory will be 2048MB+memory overhead and the slot size for CPU will be 2GHZ.

Now how does HA calculate how many slots are available per host?

Of course we need to know what the slot size for memory and CPU is first. Then we divide the total available CPU resources of a host by the CPU slot size and the total available Memory Resources of a host by the memory slot size. This leaves us with a slot size for both memory and CPU. The most restrictive number is the amount of slots for this host. If you have 25 CPU slots but only 5 memory slots the amount of available slots for this host will be 5.

The first question I got was around unbalanced clusters. Unbalanced would for instance be a cluster with 5 hosts of which one contains substantially more memory than the others. What would happen to the total amount of slots in a cluster of the following specs:

Five hosts, each host has 16GB of memory except for one host(esx5) which has recently been added and has 32GB of memory. One of the VMs in this cluster has 4CPUs and  4GB of memory, because there are no reservations set the memory overhead of 325MB is being used to calculate the memory slot sizes. (It’s more restrictive than the CPU slot size.)

This results in 50 slots for esx01, esx02, esx03 and esx04. However, esx05 will have 100 slots available. Although this sounds great admission control rules the host out with the most slots as it takes the worst case scenario into account. In other words; end result: 200 slot cluster.

With 5 hosts of 16GB, (5 x 50) – (1 x 50), the result would have been exactly the same. To make a long story short: balance your clusters when using admission control!

The second question I received this week was around limiting the slotsizes with the advanced options das.slotCpuInMHz and/or das.slotMemInMB. If you need to use a high reservation for either CPU or Memory these options could definitely be useful, there is however something that you need to know. Check this diagram and see if you spot the problem, the das.slotMemInMB has been set to 1024MB.

Notice that the memory slotsize has been set to 1024MB. VM24 has a 4GB reservation set. Because of this VM24 spans 4 slots. As you might have noticed none of the hosts has 4 slots left. Although in total there are enough slots available; they are scattered and HA might not be able to actually boot VM24. Keep in mind that admission control does not take scattering of slots into account. It does count 4 slots for VM24, but it will not verify the amount of available slots per host.

To make sure you will always have enough slots and know what your current situation is Alan Renouf wrote an excellent script. This script reports the following:

Example Output:

Cluster        : Production
TotalSlots     : 32
UsedSlots      : 10
AvailableSlots : 22
SlotNumvCPUs   : 1
SlotCPUMHz     : 256
SlotMemoryMB   : 118

My article was a collaboration with Alan and I hope you find both article valuable. We’ve put a lot of time into making things as straight forward and simplistic as we possibly can.

SRM 4.0 KB Articles

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For those looking into implementing SRM 4.0 four KB articles have been released related to SRM 4.0:

SRM 4.0 released

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VMware just released version 4.0 of SRM. Just to be clear this is not the 4th version of SRM, the version number is aligned with vCenter and ESX. I’ve highlighted the new features which I think are really really useful or exciting.

Site Recovery Manager 4.0 | 05-October-2009 | Build 192921

Release Note
New Features:

  • Full compatibility with vCenter 4.
  • Full support for NFS-based arrays.
  • Support for shared recovery sites.
    Enables many-to-one pairings of protected sites with a recovery site. For more information, see the technical note Installing, Configuring, and Using Shared Recovery Site Support, which is available at http://www.vmware.com/support/pubs/srm_pubs.html.
  • Resilience in the face of vCenter unavailability during a test recovery.
    Placeholder virtual machines can be quickly repaired after the protected site vCenter becomes available again.
  • New repair-mode installation features.
    You can run the SRM installer in repair mode if you need to change configuration parameters such as vCenter credentials, database connection information or credentials, and certificate details.
  • Graphical interface to advanced settings.
    Eliminates most requirements to edit the XML configuration file
  • Support for DB2 as an SRM database server.
  • New licensing options.
  • Improved scalability.
    A single protection group can now include up to 1000 virtual machines.
  • Full Compatibility With DPM (Distributed Power Management)
    SRM recovery plans can now power-on or power-off a host that is in standby mode.
  • New Option to dr-ip-customizer Utility
    The dr-ip-customizer utility now logs less verbose diagnostic output by default. To force dr-ip-customizer to log the same level of diagnostic output that it produced in earlier releases, use the -verbose option.
  • Change in Certificate Validation
    When you select certificate authentication, the SRM installation validates the certificate you supply before continuing. Certificates signed with an MD5 key are no longer allowed.
  • Support for Protecting Fault-Tolerant Virtual Machines.
    SRM can now protect virtual machines that have been configured for fault-tolerant operation. When recovered, these virtual machines lose their fault tolerance, and must be manually reconfigured after recovery to restore fault tolerance.
  • Improved context-sensitive Help.
  • PDF documents available on release media
    Current versions of the PDF documents for this release are available in the docs folder at the root of the SRM 4.0 CD. Updated versions of these documents may be available at http://www.vmware.com/support/pubs/srm_pubs.html.

Keep in mind that if you want to do an upgrade you need to use a specific method to be successful. It’s described here. Now go ahead, download it and try it out!

VCDX Defense Panels

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I want to stress something that not everyone seems to be aware of. Below is the “roadmap” to becoming a VCDX. Please take notice of the section on when the defense take place all the way at the bottom of the roadmap. “Interview for design defense are usually hosted at VMware events.” This means: VMworld(US / Europe), Partner Exchange etc. Keep in mind that this also means that it’s not possible to take it every month of the year. There are only a few opportunities per year to get certified, make sure you are ready!