Network storage's new safe haven: shared CD-R

Emedia Professional, August, 1998 by Robert A. Starrett

Networked CD recording, facilitated by much-evolved network software programs and hardware solutions, is an economical and technological feat whose time has come, and it's rapidly becoming the corporate storage medium-of-choice for a wide range of implementations.

CD-ROM networking is not what it used to be, and neither is networked CD recording. That's especially good news on the CD-R side, as CD recording over the network has changed to reflect new technologies that make this once-daunting process viable and stable. What's more, networked CD recording, facilitated by much-evolved network software programs and hardware solutions, is an economical and technological feat whose time has come, and it's rapidly becoming the corporate storage medium-of-choice for a wide range of implementations.

Just as the power of the Pentium processor and PCI SCSI cards have largely rendered dreaded buffer underruns a non-issue, these processors, PCI SCSI cards, and 100BaseT networking cards and hubs have enabled network operating systems to weather the rigorous data transfer demands of CD recording. But many past concerns of network recording remain relevant today. Issues like additional hardware and software costs, file server loading, server SCSI card conflicts, server device driver conflicts, user access, and user security must still be considered. However, as technology marches on, network recording becomes increasingly stable and reliable and today is remarkably accessible to many users given its early stumblings.

The advantages of recording CDs on shared drives over the network are myriad. Time was when the best argument for networking CD-R was that recorders were simply too expensive (and in the very olden days too big) to install one on every desktop, but even with the precipitous price drops we've seen CD-R take in recent years, sharing recorders among users or groups still makes economic sense. Network writing frees workstation resources for other processor and I/O-intensive tasks and allows administrators more control over CD-R security. It also lowers maintenance costs, and reduces demands on system administrators who only have to supervise one or a handful of networked recorders rather than dozens of scattered standalone CD recorders operated by users with varied technical expertise.

GOING IT ALONE

There are several physical setups that can be used to record CDs over a network that don't require additional hardware or software purchases. In a simple implementation, few additional resources are required to produce recorded discs that draw data from multiple clients or servers and bring it together in a single location for recording to CD. A recorder hosted by a local workstation with appropriate recording software can perform this job either in a batch mode that is triggered by a particular event or manually by a user assigned to record certain files to CD.

There are limitations to this as a recording solution, however. Some CD-R software still does not allow the user to designate network drives as sources. This behavior is likely a holdover from the days when network connections were not fast enough to move data across the LAN at speeds high enough to keep a CD recorder's buffer full.

In the past, attempting to record CDs over the network at speeds over 1X or during periods of increased network traffic typically yielded early buffer underruns. Thanks to today's 100BaseT connections, more sophisticated data caching techniques found in the latest networked CD management software, along with the larger internal buffers found on the latest CD recorders, a strong network should be able to sustain the data transfer rate necessary for recording at 4X and even higher speeds when 6X and 8X drives are installed.

Recording reliability can be enhanced by using the network to gather files from the server, or in a peer-to-peer situation, from the various workstations, to create a real ISO9660 image on a workstation hard drive, then transferring that image from the workstation to a local CD recorder. This works well enough if there is a spare workstation that can be dedicated to CD image creation, and if there is somebody within the organization who knows the CD-R software and has the time to produce CDs on-demand according to user requests.

But tagging files on other clients and a network server to be included in a virtual image is another matter. Several problems arise with this approach, including that some CD-R software will not allow files on a networked drive to be included in a virtual image. In many cases, the CD-Recordable software will anticipate that the transfer speed from the files over the network will be too slow to create an image on-the-fly and consequently prohibit the network files' inclusion to save the user from the buffer underrun that will inevitably result.

Even under otherwise ideal conditions, the larger the number of files included in the virtual image, the more likely it is that the process will fail. A related approach that may work better is to make a real image on a NetWare volume from server or remote client files, but this workaround only solves part of the problem, since it enables limited network writing functionality at best. This approach is more robust; with a real image, the recording process can absorb interruptions in the data stream without incurring buffer underruns since you are merely creating a hard drive file (ISO9660 image) that will later be written to a recorder on a local workstation in a single seamless write under optimum conditions. However, while you can make a disc from the real image on the file server, and avoid incurring the buffer underrun-sensitivity endemic to using a virtual image containing remote files, this approach may require that the disc be written at a slower than optimal speed.