---
title: "Erasure verification fails"
canonical: "https://support.blancco.com/space/KB/11633119/Erasure%20verification%20fails"
format: markdown
---
<span style="color: #000000">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. </span><span style="color: #000000">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.</span>

<span style="color: #000000">There are certain things that have been noticed to lessen the verification failure risk, especially in server (RAID) environments:</span>

- <span style="color: #000000">Upgrade the RAID controller firmware to the latest version.</span>
- <span style="color: #000000">Make sure that the RAID arrays are dismantled correctly before starting Blancco Drive Eraser / Blancco 5.</span>
- <span style="color: #000000">In server environments the</span>[<span style="color: #003366"> HBA may write RAID configuration information to a disk:</span>](https://go.docs.blancco.com/wiki/spaces/KB/pages/11633369)<span style="color: #000000"> 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.</span>
- <span style="color: #000000">Avoid erasing hard drives connected to multiple disk controllers, especially if the controller's are different "type" (SATA - SCSI, etc.).</span>
  - <span style="color: #000000">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.</span>
    - <span style="color: #000000">Disable or remove the additional RAID controller (preferably both) and erase the internal SATA hard drives.</span>
    - <span style="color: #000000">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.</span>

<span style="color: #000000">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):</span>

- <span style="color: #000000">Erase Samsung SAS drives on the first run.</span>
- <span style="color: #000000">Erase Seagate SATA drives on the second run.</span>

<span style="color: #000000">Sometimes a Blancco-incompatible disk/RAID controller may be the source of the issue. In a case like this, please collect </span>[<span style="color: #000000">an issue report</span>](https://go.docs.blancco.com/wiki/spaces/KB/pages/11632991)<span style="color: #000000"> and send it for Technical Support for further analysis.</span>

> Macro (__confluenceADFMigrationUnsupportedContentInternalExtension__)