Erasure verification will fail if the data samples read from a hard drive do not match the actual overwrite-data patterns that were written to the hard drive during the erasure process. Blancco Drive Eraser / Blancco 5 calculates start and end checksum, and these values are required to match. Failure in the erasure process can be caused by, for example, a mechanical failure of a hard drive or if there has been an IO level communication problem during the erasure. Most typical reasons are input/output malfunctions between the hard drive and software. The reason can be a read/write error, an electrical failure, an access error or any other type of physical hard drive failure.

There are certain things that have been noticed to lessen the verification failure risk, especially in server (RAID) environments:

Upgrade the RAID controller firmware to the latest version.
Make sure that the RAID arrays are dismantled correctly before starting Blancco Drive Eraser / Blancco 5.
In server environments the HBA may write RAID configuration information to a disk: Sometimes this can happen during the erasure process, which makes the verification checksum not match. Make sure that the automatic RAID re-building is disabled during erasures.
Avoid erasing hard drives connected to multiple disk controllers, especially if the controller's are different "type" (SATA - SCSI, etc.).
- An example: There is a server computer where Blancco Drive Eraser / Blancco 5 is booted. The server itself contains two internal SATA hard drives that are connected to the server's internal disk controller. The server also contains an additional RAID controller that is connected to a disk array that contains eight SAS hard drives. In a case like this it is recommended that the erasure is divided into two parts.
  1. Disable or remove the additional RAID controller (preferably both) and erase the internal SATA hard drives.
  2. Remove the internal hard drives or disable the integrated controller from BIOS (preferably both). Connect the additional RAID controller and make sure that the RAID controller's setup utility is able to detect the hard external SAS drives and remember to dismantle the RAID setup.

If there are still issues, try dividing the erasure process to even smaller parts. If there are multiple different hard drive models and types (an example):

Erase Samsung SAS drives on the first run.
Erase Seagate SATA drives on the second run.

Sometimes a Blancco-incompatible disk/RAID controller may be the source of the issue. In a case like this, please collect an issue report and send it for Technical Support for further analysis.