RAID, Fibre Channel reach optical storage

Posted on June 01, 2000

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New technologies may open up new application areas, but user acceptance is expected to be slow.

By Zachary Shess

For the past several years, optical library/jukebox vendors in essence have been preaching to the choir of niche markets. Unit shipments continue to decline as fewer traditional customers in document imaging, medical, and video applications purchase optical libraries to address their specialized needs.

And the relegation of optical devices to secondary storage roles in IT environments has caused vendor defections. For example, in the last 18 months, Sony exited the magneto-optical (MO) library market and Cygnet Storage Solutions sold off its write-once read-many (WORM) optical business to Plasmon.


Figure 1: High availability is achieved using a 4+1 configuration, in which one optical drive is dedicated to parity.
Click here to enlarge image

However, recent technology developments in optical storage may finally address some of its deficiencies, while satisfying expanding application and capacity requirements generated by the gigantic amount of digitized audio/video files and Web-based content.

One new technology is optical RAID. At this spring's NAB and AIIM shows, DVD-RAM library vendors Asaca Shibasoku Corp. of America, Cygnet Storage Solutions, and Disc Inc. demonstrated optical RAID capabilities based on controllers from Ultera Systems. In addition, Maxoptix has demonstrated its MaxRAID MO towers with the Ultera Striper 3 series controllers. These demonstrations marked the first time that optical storage devices have been able to leverage the increased performance and fault-tolerance benefits of RAID technology.

Another hope for an optical comeback rests on the possibility that libraries may soon be deployed in storage area networks (SANs) via Fibre Channel attachments. So far, SAN-based storage and backup/archival devices have consisted primarily of disk arrays and tape libraries. However, Hewlett-Packard in April announced that its HP SureStore E MO libraries support point-to-point Fibre Channel connectivity.

Optical storage vendors readily admit that libraries have suffered from relatively slow transfer rates and a lack of software to span files across multiple discs or libraries, a characteristic of RAID. Both of these drawbacks have hampered widespread adoption in mainstream data centers.

"You were limited to the file size that could fit on one side of the media. So to accommodate streaming video, for example, we needed a larger file capacity that could span across disks," says Chris Stone, Asaca's U.S. director of sales and marketing.

Optical RAID

Armed with traditional RAID benefits, optical library vendors now believe their devices can reach new markets. Similar to traditional hard disk arrays, striping data across DVD-RAM or MO drives in a single library, or across up to five libraries, improves data transfer rates because the drive group or libraries appear as a single entity to the host server (see Figure 1). By grouping a four-drive RAID set with a parity spare, transfer rates can be increased up to 4x. The Ultera Striper 3 controllers offer support for RAID-0, RAID-1, or RAID-3 configurations.

The Ultera controller can also operate with five libraries as though they were a single library directly attached to the server (see Figure 2). This configuration is sometimes referred to as a redundant array of independent libraries (RAIL).

To increase fault tolerance, especially with larger capacities, RAID-1 mirroring can provide redundant array protection. Five copies of data can be created simultaneously.


Figure 2: An optical RAID controller can operate five optical libraries in a 4+1 configuration that appears to the backup server as a single device.
Click here to enlarge image

The optical library array and controllers identify which piece of media corresponds with the proper RAID set, and write data from removed-and then replaced-media back in the correct RAID configuration.

"A traditional RAID controller does not expect a disk to get up and walk away," says Fred Bedard, Ultera's vice president of sales and marketing. "However, when you eject optical media and take the RAID set out, the controller now needs to know that media can be removed. When the media is replaced, the data needs to be back in the same order."

New applications

Optical RAID also helps increase library capacities, which may open up new applications. With RAID sets able to group drives and/or libraries, libraries can be logically grouped together to appear as a multi-terabyte system.

"Users are considering optical RAID for large applications with high volumes of data and large data blocks, such as video streaming and Internet applications with high-resolution graphics," says Wayne Augsburger, vice president of sales and marketing at Cygnet. "With optical RAID, you have a good transfer rate and essentially much larger media capacity because you're looking at four times the capacity."

Industry analysts, including Data-quest's Mary Craig, also see the potential for optical storage being used in backup applications. However, Craig does not anticipate overnight adoption. "I think it's going to take some education, and some users will want to see it proven first. Traditionally, backup is done with tape, so it's going to take some time to get administrators to take optical seriously for backup applications. RAID technology provides about the only chance that optical can be used for backup," Craig says.

Fibre Channel connectivity* While RAID-equipped optical libraries will soon make their way into customer sites, widespread connectivity via Fibre Channel to SANs may be a couple years away. Hewlett-Packard recently announced Fibre Channel attachment for its SureStore E MO libraries. However, HP will initially offer only point-to-point connection via a SCSI-to-Fibre Channel router. Fibre Channel connections for arbitrated loop and switched fabric topologies are due later this year.

HP officials and industry analysts acknowledge that early demand will not be high, but both expect some interest for specialized applications that require longer connection distances. Like libraries equipped with optical RAID, Fibre Channel connectivity is not expected to generate widespread interest until optical devices are considered to be viable backup solutions for SAN environments. For that to happen, arbitrated loop and switched-fabric support is necessary.

"To just provide a jukebox with a Fibre Channel connection does not solve anyone's problems," says Mike Peebles, HP's MO product manager. "When we start having multiple hosts that have the ability to access a common jukebox in SAN environment, that's when the benefits of shared resources will be worth the investment."

The industry's other MO vendor, Maxoptix, currently does not have specific plans to connect its libraries or towers to Fibre Channel. David Kalstrom, vice president of marketing at Maxoptix, says the company at this time is focusing primarily on delivering initial shipments of its Optical Super Density drives and media later this year.

Analysts and vendors agree that RAID technology and Fibre Channel connectivity are not magic elixirs that will quickly cure the woes of the high-end optical storage market. However, both technologies present some potential for optical libraries to address problems across a broader scope of applications.


Medical industry embraces DVD
Medical software vendor uses DVD-R libraries in its turnkey cardiology imaging network.
By Zachary Shess

DVD proponents have touted the technology's ability to deliver high-capacity, random file access with vastly improved image resolution. While technology benefits always seem to be translated into cost and time savings, one software company is coupling its technology with DVD to help heart patients experience real life savings.

Storage administrators at 2,300 cardiology labs nationwide face rapidly increasing capacity and business-critical requirements for secure, reliable file access. They also have concerns about costs and the ability to manage data across divergent file systems.

Cardiologists have recently benefited from a number of technological advances, such as the ability to diagnose heart problems by inserting miniature 35mm cameras into patients' arteries. However, once these images are placed on film, new management challenges emerge. While the Digital Imaging and Communication in Medicine (DICOM) standard has provided medical imaging device manufacturers with an interchange method for managing various types of image files, no standard has been established for how to best store these images and make them ready for easy, fast access to medical staff.

While DVD technology has yet to gain widespread adoption, its high resolution has won over users in some applications, none more critical than helping diagnose heart conditions. In addition to providing clearer images, DVD helps cardiologists retrieve data more quickly than other optical technologies. In addition, with DVD's increased capacities, more data can be kept on the network.

Heartlab Inc., a Westerly, RI-based software developer and systems integrator, provides a turnkey system for cardiology labs that eliminates film and replaces it with higher-resolution digital images. On the software side, the DICOMview Cardiac Network, installed in more than 600 labs worldwide, includes proprietary Windows NT-based cardiac imaging software that digitizes a patient's cardiac test results. Once the DICOMview Angiographic Review software chronicles a patient's condition, DICOMwriter software facilitates file access from the storage devices.

The suites are bundled with a network of Dell servers and workstations equipped with special high-resolution monitors. By networking devices over Gigabit Ethernet or ATM, medical staff can view patients' results right from the emergency room, saving critical time.

The servers and workstations access stored files via SCSI from a FlexLibrary DRM-7000 recordable DVD (DVD-R) library from Pioneer New Media Technologies. The FlexLibrary series holds up to 670 DVDs, or 3.2TB-enough capacity to store approximately 14,000 patient records.

From the company's inception in 1994 up until last year, Heartlab Inc. archived data on DLT tape libraries. When Heartlab president Robert Petrocelli was approached in early 1999 to consider DVD, he was skeptical. However, after a one-year beta test pitting DVD-R against DLT tape, as well as other optical technologies, Petrocelli changed his mind and began installing DVD-R libraries in the DICOMview Cardiac Network.

On average, cardiology labs spend about $58 on film for each patient. Petrocelli claims that by using DVD-R media, its cardiac system should cost a lab less than $30 per case. Additionally, Petrocelli says the cost of providing 3TB of DLT storage is about 30% higher than DVD-R.

Heartlab also found value in DVD-R's random access capabilities and retrieval speed. For example, archival speeds went from about five minutes to less than one minute. Engineers also tested magneto-optical and DVD-RAM, but found the read/write performance to be slower than DVD-R.

However, the ultimate value of DVD-R as part of a specialized cardiac network is its ability to provide doctors with critical diagnostic information quickly and reliably. During a recent installation, as Heartlab technicians were in the process of transitioning a cardiology lab off film and onto the cardiac network, Petrocelli says a cardiologist was able to locate a lesion on a heart valve that he hadn't seen. In the end, that patient made a complete recovery.


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