Dario IT Solutions Blog

I’ve summarized several notes about Hyper-V and VMM. It may be useful for you to take it into account when planning or handling Hyper-V platforms.

1. Enabling NLB on a VM
Follow this procedure in case you need to enable NLB on a VM running under Hyper-V 2008. http://support.microsoft.com/kb/953828
Note that when your VM is running under Hyper-V 2008 R2, you will no longer need to specify a certain MAC. You will only need to check the option to “Enable MAC spoofing”.
Follow this link for detailed steps: http://robwhitehouse.com/virtualisation/enable-nlb-in-a-hyper-v-guest/

2. Max CPUs per VM
This Technet article shows the max number of allowed CPUs per VMs : http://technet.microsoft.com/en-us/library/cc794868(WS.10).aspx

3. Disk alignment
Set the disk alignment on two levels:

1. On the storage level. Set the alignment of the LUN so that the disk that the Host OS sees will see blocks the same as you storage device.
   Follow this link for best practices for Hyper-V on NetAPP : http://www.netapp.com/us/communities/tech-ontap/tot-hyperv-best-practices-0911.html
   Follow this direct link for the complete document, where you will find additional information regarding disk alignment : http://media.netapp.com/documents/tr-3702.pdf
2. Within the VHD. After aligning the partition on the LUN on the Host server, you should also align the partition that exists within the VHD file. The above link to the NetAPP documentation shows this procedure as well. You should notice, though, these point:

i. 2008 R2 allows you to mount a VHD to the host (without booting it to a VM). This allows you to create / change / align partitions from the host itself, before creating the VM.

ii. Aligning the VHD is only relevant for fixed virtual disks. Alignment of Incremental or dynamic disks won’t last, due to the nature of the file.

4. IDE / SCSI
Your boot disk has to be connected to an IDE controller on the VM (SCSI controller is a synthetic device http://technet.microsoft.com/en-us/magazine/2008.10.hyperv.aspx?pr=blog ). Connect all Other drives to a SCSI controller for better performance.controller.

5. Pass Through Disks
For best application disk performance, use Pass-Through disks. Pass-Through disks will give the VM direct access to a physical drive. For more information on this feature: http://technet.microsoft.com/en-us/library/cc768521(BTS.10).aspx

6. Moving VMs from 2008 to 2008 R2
After moving VMs from a Server 2008 to Server 2008 R2 be sure to install the integration services again.

7. General Host / VM Performance
Follow this link for explanation about measuring basic Memory / CPU / Disk performance: http://technet.microsoft.com/en-us/magazine/2008.08.pulse.aspx?pr=blog . Pay special attention to the disk monitoring. It is very likely that you’ve placed several disk intensive VMs on the same LUN.

8. Disconnect ISO files
When working on a Hyper-V cluster, make sure that you disconnect any ISO file from a VM when you’re done using it. Otherwise, when moving or live migrating your VM, it may fail because it wouldn’t find the ISO to connect to on the other node.

9. What’s new in VMM 2008 R2
http://www.microsoft.com/systemcenter/virtualmachinemanager/en/us/whats-new-r2.aspx

10. Disk size planning
When planning the size of the disk holding the VM’s VHDs, make sure that you have enough free space to save also the VM’s snapshots and entire memory. When Saving / Moving or Live Migrating the VM, the VM’s entire memory content is saved to disk.

Related posts:

1. Hyper-V Deployment – Notes from the field
2. Windows Server 2008 Hyper-V Storage
3. Booting an Hyper-V guest from an iSCSI LUN
4. Performance on Hyper-V
5. Important notes on VMM 2008