Friday, December 3, 2010

Refreshers in SCVMM

As I have mentioned in some of my previously posts – the most accurate information about your Hyper-V hosts and Failover Clusters will be presented in Hyper-V Manager and Failover Cluster Manager.

I have often seen that the information that SCVMM presents, is misleading and not trustworthy.
So I will explain the refreshers in SCVMM in this post.

SCVMM periodically collects info from your hosts and library servers and compares tem with knowledge that already exists in the database.
The changes that are detected will be updated, and an audit log is created in the job view in SCVMM console.
The refresher times are customizable but the info about ‘how-to’ is not made public since the impact on performance to the virtualized environment is considerably.

You can off course manually refresh the status of an object.

VM Properties Refresher

It runs every 2 minutes on every host and does the following:

1)      Checks the host for successful connections through WinRM
2)      Checks the status of all the VMs residing on that host
3)      Marks a VM as missing if it no longer exists on the host
4)      Imports newly discovered VMs from the host if they do not exist in VMM

VM Refresher

This is the ‘heavy’ refresher, and runs every 30 minutes on every host and does the following:

1)      Refreshes all the virtualization information for all VMs on the hosts. (Settings, disks drives, storage,DVD, Network, clustering (HA)
2)      Refreshes FC, ISCSI for every VM
3)      Refreshes snapshots information and differencing disk information for each VM

Host Refresher

This refresher also runs every 30 minutes on every host and does the following:

1)      Updates host properties and status
2)      Updates physical disks and SAN information
3)      Updates networking (physical NIC, and vNICS)

(This refresher will not update any information for hosts that are in maintenance mode in VMM)

Library refresher

Runs default every 1 hour, but a user can configure this to run max 336 hours. This refresher can also be turned off completely. It does the following:

1)      Updates library shares that are under management in VMM
2)      Detects new library objects, changes, and marks objects as missing if they can no longer be found in the library
3)      Finds and imports any offline or stored VM in the library that were not already under management

Cluster refresher

Runs every 30 minutes and does the following:

1)      Refreshes all cluster related properties that is displayed in VMM, also available storage for creating new HA VMs.
2)      Adds newly added cluster nodes
3)      Removes removed cluster nodes

Performance refresher

Runs every 9 minutes on every hosts or whenever there is any state changing operation on the VM.
It collects counters information for both hosts and VMs on them.

Tip: Do not always rely on the information presented in SCVMM, but double check with your Hyper-V Manager and Failover Cluster Manager. If there is always misleading information in SCVMM, it may be a reason for troubleshooting this.

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