Jasmine McTigue

Network Computing Blogger

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Where the Cloud Touches Down: Simplifying Data Center Infrastructure Management

Thursday, July 25, 2013
10:00 AM PT/1:00 PM ET

In most data centers, DCIM rests on a shaky foundation of manual record keeping and scattered documentation. OpManager replaces data center documentation with a single repository for data, QRCodes for asset tracking, accurate 3D mapping of asset locations, and a configuration management database (CMDB). In this webcast, sponsored by ManageEngine, you will see how a real-world datacenter mapping stored in racktables gets imported into OpManager, which then provides a 3D visualization of where assets actually are. You'll also see how the QR Code generator helps you make the link between real assets and the monitoring world, and how the layered CMDB provides a single point of view for all your configuration data.

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A Network Computing Webinar:
SDN First Steps

Thursday, August 8, 2013
11:00 AM PT / 2:00 PM ET

This webinar will help attendees understand the overall concept of SDN and its benefits, describe the different conceptual approaches to SDN, and examine the various technologies, both proprietary and open source, that are emerging. It will also help users decide whether SDN makes sense in their environment, and outline the first steps IT can take for testing SDN technologies.

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Recovering From RedoLog Corrupt Errors On VMware ESX/ESXi

In my last entry, I discussed basic best practices for using snapshots in VMware environments. Today I want to get a little more technical by talking about recovery options for virtual machines which will not boot because of snapshot errors.

When you issue a delete all snapshots from the context menu of the Virtual Infrastructure (VI) client, if the disk space is insufficient to complete the operation, VMware has a nasty tendency to remove the physical snapshot files (.vmx) and leave you with a non-functional VM without any snapshots listed. When you try and power on the virtual machine in question, you will get the familiar: "The RedoLog for "SERVERNAME" has been detected to be corrupt. The virtual machine needs to be powered off. If this problem persists, you need to discard the RedoLog."

Unfortunately, because you already tried to reconcile snapshots with insufficient disk space, there are no longer any .vmx files on the datastore and there are no snapshots listed in the snapshot manager. Because of this, you can no longer issue the "remove all snapshots" command from the VI Client and consequently can't fix the problem from the VI client GUI.

Start by freeing up space on the datastore equal to the total size of the disks attached to the VM. Sit down at the console or start up an SSH session to your ESX host. Change directory to the datastore and virtual machine folder in question. The disks for the fragmented VM will be split into as many different files as there are snapshots. In order to repair the disk files, we need to clone the fragmented disks to a new file. Run the command:

vmkfstools -i vmname.vmdk vmname-repaired.vmdk

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