Happy New Year
Happy New Year to everyone!
I passed the VCP on vSphere 4 just before Christmas with 463/500. At the time the deadline for taking the exam without having to the attend the What’s New was 31st December 2009, but that’s now been extended to the 31st January. It was nice to have it out of the way before Christmas though.
The exam seemed no more difficult than the VCP on VI 3; I think they even reused a few of the questions. I found the following useful:-
- Simon Long’s VCP vSphere 4 Practice Exams
- vSphere 4 Configuration Maximums
- Barry Coombs’ VMware vSphere cue-cards
Those sites also contain numerous links to other resources, so I’m sure you’ll find something which will suit your revision style.
Next on my to-do list is the Microsoft 70-431 Microsoft SQL Server 2005 – Implementation and Maintenance.
vSphere 4.0 Update 1 Released
VMware have released update 1 for vSphere 4.0.
The following enhancements have been made to ESX (from the release notes):-
VMware View 4.0 support – This release adds support for VMware View 4.0, a solution built specifically for delivering desktops as a managed service from the protocol to the platform.
Windows 7 and Windows 2008 R2 support –This release adds support for 32-bit and 64-bit versions of Windows 7 as well as 64-bit Windows 2008 R2 as guest OS platforms. In addition, the vSphere Client is now supported and can be installed on a Windows 7 platform. For a complete list of supported guest operating systems with this release, see the VMware Compatibility Guide.
Enhanced Clustering Support for Microsoft Windows – Microsoft Cluster Server (MSCS) for Windows 2000 and 2003 and Windows Server 2008 Failover Clustering is now supported on an VMware High Availability (HA) and Dynamic Resource Scheduler (DRS) cluster in a limited configuration. HA and DRS functionality can be effectively disabled for individual MSCS virtual machines as opposed to disabling HA and DRS on the entire ESX/ESXi host. Refer to the Setup for Failover Clustering and Microsoft Cluster Service guide for additional configuration guidelines.
Enhanced VMware Paravirtualized SCSI Support – Support for boot disk devices attached to a Paravirtualized SCSI ( PVSCSI) adapter has been added for Windows 2003 and 2008 guest operating systems. Floppy disk images are also available containing the driver for use during the Windows installation by selecting F6 to install additional drivers during setup. Floppy images can be found in the /vmimages/floppies/ folder.
Improved vNetwork Distributed Switch Performance – Several performance and usability issues have been resolved resulting in the following:
- Improved performance when making configuration changes to a vNetwork Distributed Switch (vDS) instance when the ESX/ESXi host is under a heavy load
- Improved performance when adding or removing an ESX/ESXi host to or from a vDS instance
Increase in vCPU per Core Limit – The limit on vCPUs per core has been increased from 20 to 25. This change raises the supported limit only. It does not include any additional performance optimizations. Raising the limit allows users more flexibility to configure systems based on specific workloads and to get the most advantage from increasingly faster processors. The achievable number of vCPUs per core depends on the workload and specifics of the hardware. For more information see the Performance Best Practices for VMware vSphere 4.0 guide.
Enablement of Intel Xeon Processor 3400 Series – Support for the Xeon processor 3400 series has been added. For a complete list of supported third party hardware and devices, see the VMware Compatibility Guide.
vCenter 4.0 has also been updated, and now has full compatibility with Windows 7 x86 and x64 versions. Saving the various hacks that were necessary to get it working.
Also, the PowerCLI has been updated, and can be found here. There are 68 new CMDLETS, which Alan Renouf does a great job of explaining. I’m especially looking forward to trying out Get\Set-CustomAttribute (no more manipulation of the View object), Move-VMTemplate (no more converting templates to machines), and Get\Set-VMQuestion (for those times when the datastores run out of space for the REDO files necessitated by Non-Persistent disks).
I’m looking forward to investigating the new PowerCLI functionality, and I’m also looking forward to not needing to manually customise the dozen or so Windows 7 guests I’m deploying next week!
Alpha build of Project Onyx
Carter Shanklin has announced that VMware have released an Alpha build of the long-anticipated Project Onyx. This is a script recorder for vSphere Client, which is designed to allow scripting of things which are awkward or difficult to achieve using the VMware PowerCLI APIs alone.
Downloading this at the moment, although I don’t suspect I’ll have time to look at it for a while.
Understanding Memory Resource Management in VMware ESX Server
Photo from Flickr, courtesy C Wood
VMware have published an excellent white paper on memory management [pdf].
The document is technically detailed, but makes interesting reading. The authors do a good job of describing the methods ESX uses to manage and allocate virtual memory; and how when guests deallocate memory it’s not necessarily freed up for reuse by other guests. This should prevent you from allocating more memory to guests than is physically available on the host (overcommitting); however the hypervisor uses three memory reclamation strategies which allow overcommitment:-
- Transparent Page Sharing (TPS). Where ESX detects that multiple guests are using identical memory pages (such as those used by common OS components), it presents one shared copy to the guests. By default, this is active all the time. If the guests need to write to the memory, a copy needs to be made, which incurs a slight performance penalty.
- Ballooning. Is where VMware tools allows the hypervisor to see inside the guest operating system and reclaim unused memory. This typically occurs when ESX drops to less than 4% free memory (the Soft threshold). It has more of an overhead than TPS, but is still preferable to the alternative.
- Hypervisor swapping. This is used as a last-resort when TPS or Ballooning cannot provide enough memory (or cannot provide it quickly enough). Swapping tends to affect the guest more than the other two methods.
In the unlikely event that Hypervisor Swapping is unable to provide enough memory to meet the requirement, the hypervisor blocks the execution of all virtual machines which exceed their memory limit.
The whitepaper details the results of various benchmarks to evaluate the performance overhead of each of the reclamation strategies. While I’d certainly heard that the performance impact of TPS was negligible, I had always been slightly sceptical, but the data provided by VMware would appear to back it up.
The whitepaper also includes some best practices for memory management, some of which have had me thinking about our memory allocation strategy:-
- Do not disable page sharing or the balloon driver. These two techniques are enabled by default in ESX4 and I can’t imagine that anyone would disable them unless they had specific reason to. It’s also another reason to make sure you have VMware tools installed on all your guests.
- Carefully specify the memory limit and memory reservation. Our environment is pretty fluid, with a large number of small guests with 10-15% of them being . For this to be useful for us, these values would need to be constantly checked and reconfigured.
- Host memory size should be larger than guest memory usage. I generally try to limit our hosts to a 20% potential overcommit on RAM allocated to guests, and as there are usually only about 80% of our machines switched on at any one time, the hosts are normally pretty comfortable. However, this conservative approach means our RAM allocations need to be carefully managed, and kept as low as possible; which may be hitting us elsewhere (see below)
- Use shares to adjust relative priorities when memory is overcommitted. Our environment is pretty unique in that the vast majority of the machines have equal priority, so there’s little need for us to add another management overhead.
- Set appropriate Virtual Machine memory size. The virtual machine memory size should be a little larger than the average used by the guest. I think this is an area we need to look at in our environment. Our default RAM allocations for guests is probably a little on the low side, due to historical reasons, and due to our current environment being configured with a rather paltry 16GB of physical RAM (a problem that will be resolved in the next couple of months). We may be keeping our memory usage in check, but the resultant disk-swapping might be stressing our storage infrastructure.
The white paper is definitely worth reading; it’s certainly going to help me plan a memory management strategy for the implementing our infrastructure on the new hardware .
Training resources for VCP on vSphere 4.
Vladan Seget has posted some links to training resources for VCP on vSphere 4.
It doesn’t look like I’ll have time to do the upgrade course this year, which means, as a VCP ion VI3, I won’t be eligible to bypass the “What’s New” course (see below).
VCP on vSphere certification now available
The VCP on VI4 certification is now available.
Registration for the VCP4 exam will open on August 14th. The first exam date available will be August 25th.
VMware Developer CodeCentral
VMware have launched a new community site for code examples, and there’s a section on VMware vSphere PowerCLI (formerly VI Toolkit).
They seem to be picking the best scripts from the regular contributors to the forums, so it’s a good place to have a look for examples. They’re rated by users, and tend to be slightly better documented than the ones posted in the forums (which tend to be appended and amended as the thread progresses).
I/O Queues, “micro-bursting”, and Multipathing
Virtual Geek has an interesting article on VMware I/O queues, “micro-bursting”, and multipathing.
Looks intimidating at first glance, but it’s suprisingly straightforward.
Xtravirt White Paper on Storage Oversubscription Technologies
Is your storage overcrowded?
Excellent white paper from Xtravirt detailing advantages and disadvantages of linked-clones, thin-provisioning, and data-deduplication in order to pack more VMs onto your storage.
Storage Oversubscription Technologies | Xtravirt (registration required).
vSphere Evaluator’s Guide
Eric Siebert at vSphere-Land.com points out that VMware have published a 120-page vSphere Evaluator’s Guide that’s chock-full of information about the new features (including a nice little demo of PowerCLI).
Definitely worth checking out.
