VMware releases bugfix for change block tracking (CBT) data corruption

VMware released on January 27 an important patch for vSphere 5.0, 5.1 and 5.5. This fixes a bug in Change Block Tracking which could lead to customers not being able to restore virtual machines due to missing blocks!

Make sure to apply this patch if you are using CBT and expanded the size of virtual disks!

This issue occurs when you expand a virtual disk .vmdk file which has Change Block Tracking (CBT) enabled past any 128 GB boundary. When the disk is extended the change tracking data becomes unreliable. Due to the faulty changed block information, some changed blocks might not be captured by a backup. Consequently, a restore operation that uses the incomplete backup could cause a data loss. More information here.

The issue is described by Symantec here. A lot of discussion about this issue in the Veeam forum.

Veeam has a KB article about the CBT corruption.

The patch is VMware ESXi 5.5, Patch ESXi-5.5.0-20150104001-standard (2099271) and more information can be found here.

The description of the fix is:

When you use backup software that uses the Virtual Disk Development Kit (VDDK) API call QueryChangedDiskAreas(), the list of allocated disk sectors returned might be incorrect and incremental backups might appear to be corrupt or missing. A message similar to the following is written to vmware.log:

DISKLIB-CTK: Resized change tracking block size from XXX to YYY

For more information, see KB 2090639.


Free Oracle on VMware Licensing webinar

I wrote quite a few blogs on licensing Oracle on VMware. Mainly because there is a lot of misunderstanding/FUD and Oracle let customers pay for something they do not have to pay for. Best example is the statement of many Oracle sales people that a complete VMware cluster needs to be licensed for Oracle, even if Oracle VM’s will never run on all of the nodes. As a result customers create a seperate VMware HA cluster for Oracle VM’s.

An overview of my posts on Oracle licensing can be found here. 

At March 19 there is a free webinar on Oracle licensing with experts like Dave Welch and Daniel Hesselink. Very much recommended!

Basically Oracle behaves like a corrupt policeofficer in a dodgy country stopping your Ferrari and telling he will fine you just because your car is able to drive 300km/h. No prove you actually drove faster than allowed.


One of the best videos in which an Oracle employee explains subclustering is this one. The video was deleted from the VMworld.TV site within 24 hours on request by Oracle. Guess why? Because Oracle tactics is to be so unclear as possible about licensing.

At March 19 there is a great webinar on Oracle licensing for VMware.

VMware, in partnership with DBTA, has invited the world’s most recognizable experts in this subject to join us on a webinar for a frank and direct conversation about how to properly adhere to existing contracts, as they exist presently and are available publicly, to correctly license virtualized infrastructure for Oracle.

Please join us as Don Sullivan moderates a discussion on this subject with globally renowned subject matter experts Dave Welch of “House Of Brick” and Daniel Hesselink of “License Consulting”

Register here.