Unqualified

Paul Crowley is the founder and lead developer at InfinaDyne.  He has worked with optical media devices since 1994 for a variety of different tasks, including the collection of evidence for civil and criminal prosecution.  Mr. Crowley is the author of the book "CD and DVD Forensics".

Introduction

A problem faced by all computer forensic examiners is deciding if the CD or DVD drive they are using is "qualified", that is to say if the drive is going to give the best possible results and no false data.  There are a number of factors which influence this, only some of which are obvious to the examiner.  Of course it would be nice to know a brand name which represents the highest quality, but even with things where there are clearly defined brands such as cars, you would not use the a Mercedes when a Hummer was more suited to the task.

Today, there are a large variety of CD and DVD drives available but they all share a single common market - consumers.  There are virtually no "professional" drives, drives that might cost more but are manufactured to higher standards.  Most of these drives share nearly identical characteristics in that they are not terribly bad nor terribly good.

One drive stands out far above others for processing CDs of all types - Plextor PX-W1210T or PX-W124T.  These drives are the finest that we have encountered for reading marginal CDs, barely readable CD-RWs, damaged CD-Rs and so on.  We regularly receive discs from consumers that cannot be read on their hardware.  Placing the disc in one of these drives almost always results in a completely readable disc.  They are so good at what they do we sell them to professionals looking for an unbeatable drive for reading problematic discs.

 We have yet to find as good a drive for DVD media.  So far, earlier Plextor drives (such as the PX-740) and Pioneer drives (such as the DVR-110) have shown themselves to be good.  However, the Pioneer drives are not without their difficulties.

Unqualified Drives

Unfortunately, there are a number of drives which need to be identified to forensic professionals.  These drives return incorrect data in one fashion or another and this makes their use for forensics unacceptable.

Pioneer DVR-100 through DVR-112
Pioneer DVD drives have the characteristic of returning random data for certain sectors that other drives return as unreadable.  The result is an ever-changing MD5 hash value for discs that have these unreadable sectors present on them.  While these drives are good for reading DVDs, they should not be used for CDs at all.  If you require a single drive for both types of media, it is recommended that you avoid all Pioneer drives.
We have continued to check with Pioneer support to no avail.  This is clearly a firmware issue that could be fixed for all drives in the series.  If this situation changes we will be happy to strongly recommend these drives.
LiteOn LH-2B1S (Blu-Ray)
This is the first Blu-Ray drive that we have evaluated, but the problems with it are so severe that it deserved to be listed here.  When reading sequential sectors on CD-R media any link blocks created with TAO writing cause major problems in addressing.  The result is that the sector numbers no longer match up with the correct sectors.  This completely distorts any data returned from this drive and will result in incorrect MD5 hashes or even the inability to process the file system present.  We have communicated this to LiteOn support and are waiting on their reply.