There are two broad families of DVD-recordable technology, known as DVD-R and DVD+R. Since roughly 2006, every computer DVD writer/recorder has been able to read and write both formats. Since the two formats became ubiquitous on both devices, the term has drifted a bit and includes hard-drive based DVRs with DVD recording capabilities.
In its original incarnation, the term “multi-drive recorder” meant that the device could write and read both formats; this used to be a significant technical hurdle, as the older DVD-R standard required different manufacturing technology on the discs themselves. DVD-R came out in 1997, while DVD+R came out in 2004. Because of advantages in error prevention, DVD+R has since become the default recording technology.
Initially, the discs for DVD-R and DVD+R technologies were incompatible. By late 2007, both devices were reading and writing to the same media type, and as of 2013, you won’t find a disc that won’t work in either format. You may run into compatibility issues when trying to play discs that were recorded prior to the two formats becoming more or less one standard, but this unlikely. DVD-R disks are slightly more compatible with older hardware; they also store 6MB more data per layer on the disc.
The rise of TiVo, and then the creation of new versions of DVRs from different vendors came at about the point where the DVD-R and DVD+R standards became low-cost features and DVD recorders had largely become commodity consumer electronics. As a result, most DVRs came with DVD players and DVD recording systems built into them.
Hybrid DVR-DVD recorders were also called “Multi-Drive DVD Recorders” by some manufacturers, and had the advantage that you could record your programs to a DVD for later archiving. These are still made, though the rise of streaming services like Netflix is reducing their appeal.
Multiple Disk DVD Duplicators
The last type of multi-drive DVD Recorders are professional DVD-R duplicating machines. While most home users can easily burn a single copy of a DVD, professional duplication services have machines that load the disk image onto a hard drive, and burn the file to anywhere from 5 to 300 discs at the same time, depending on their configuration and underlying hardware. These systems aren’t cheap and typically run several hundred dollars for the low-end models, and go up quickly from there.