Ready to play
- By J.B. Miles
- Oct 30, 2002
MO, CD and DVD jukeboxes are up to near-line storage tasks
Powerfile Inc.'s C200S, priced at $5,999, holds up to 200 DVD-ROM disks and 1T of data.
Government agencies will never face a shortage of data'it pours in daily, ballooning storage requirements and complicating the task of tapping that data for online services.
They do have shortages in funding and skilled IT personnel, so adding more administrators to handle the task isn't often an option. But using high-end storage devices, including the 5.25-inch optical jukeboxes included in this guide, could be.
An optical jukebox contains drives and storage shelves that can hold up to thousands of optical disks. When a user opens a file, a request for information goes to a software indexing system, which identifies where the information is stored. Almost instantly, a robotic arm or autochanger speeds to the appropriate disk and places it into a drive. The drive then reads the data off the disk and routes it back to the user.
Small optical jukeboxes contain one to six drives and handle 50 to 200 disks. Big boxes contain 48 or more drives that handle thousands of disks. Another quarter
As more drives and disks are added to a base system, some optical jukeboxes can be scaled to handle between a few hundred gigabytes to 10T of data, depending on the types of media used.
Optical jukeboxes often are part of a document and image management system that includes a scanner, PCs and workstations, monitors, software and a printer.
When a document is scanned into a document management system, it is digitized by application software residing on the workstation and written onto an optical disk within the jukebox by a writable magneto-optical (MO), CD or DVD drive. The disk is then indexed and stored for retrieval.
In such cases, optical jukeboxes become repositories of data for near-line storage.
Near-line storage is for files that are accessed less frequently than those stored online'such as on the hard disk of a workstation. Data stored on a hard drive can be retrieved within milliseconds, but there is generally a delay of 10 to 30 seconds in near-line data retrieval using an optical jukebox.
Three types of 5.25-inch optical jukeboxes dominate the market:
Multifunction MO. These jukeboxes use the 5.25-inch form with 130mm disk cartridges. Typically highly scalable, high-capacity systems, they offer both rewritable and permanent (write once) data storage and retrieval. MO disks offer capacities of up to 9.1G, and the drives used by most MO jukeboxes offer backwards-compatibility with earlier 5.2G disks.
MO technology is noteworthy for its stability and robustness. Mean swaps between failure (MSBF) is a reliability measure of jukeboxes in general, and MO devices consistently offer better ratings than competing CD and DVD devices.
Hewlett-Packard Co. and Plasmon, which together accounted for almost 95 percent of the MO jukebox market last year, claim MSBF ratings of at least 2 million. The MSBF rating of Plasmon's extensive G-Series of MO devices is the industry's highest, at 3.8 million.
The economic downturn, along with the terrorist attacks last year, has hurt the market for MO. And many MO drive suppliers have dropped out of the market, leaving only a few players capable of providing the 14X 9.1G drives. Many potential buyers seem to be waiting for higher-capacity MO technology.
Writable CD. CD jukeboxes offer relatively low capacity but permanent storage on a dependable medium. CD-ROM disks can be used for data archiving when cost is a factor. Write-once CD-R drives and rewritable CD-RW drives can use both 650M CD-ROM and CD-R disks, but generally offer slower retrieval times than do MO and DVD drives.
But when storage requirements are in the gigabyte range and retrieval volumes are light, CD jukeboxes can be the best solution for cost-conscious managers.
Writable DVD. Like MO and CD, DVD technology offers both rewritable and permanent storage. A double-density DVD-ROM disk can hold a whopping 17G of storage, almost twice that of a high-capacity MO disk. Write-once DVD-R disks have 4.7G of storage capacity and the security of data that can't be changed. Writable DVD-RAM, the most popular writable DVD format to date, has 5.2G of storage per disk.
Competing standards have held back the market for DVD in general'except at the popular consumer level'and the drives and robotic arms of both DVD and CD products tend to be less robust than MO systems, which makes them less suitable than MO for high retrieval volumes.
Nevertheless, if you don't need mission-critical performance, rewritable DVD jukeboxes could do the job.
Several companies recently released enhanced CD-ROM and DVD-ROM jukeboxes with both record-once and rewritable options.
Optical jukeboxes have many advantages for near-line storage. They are highly scalable and increasingly dependable. They can store and retrieve many terabytes of data relatively quickly. Write-once media ensures data security, since once data has been written it can't be erased. The disks themselves have a very long shelf life and are impervious to dust and magnetic corruption. Multiple drive types with different read/write capabilities can be used within the same box in the newest systems.No common language
But a standards struggle still plagues the optical industry, particularly in the DVD arena. MO media can't be read by a CD or DVD system, and vice versa.
Competing and very effective storage technologies such as RAID arrays and magnetic tape are already in place at most sites and offer competitive performance at often significantly lower prices than optical. For example, a RAID array stores and retrieves data in about 10 milliseconds, compared with about 10 seconds for an optical jukebox. And prices for RAID systems are dropping yearly.
Though tape subsystems generally take even longer to retrieve data than optical systems, they cost less per megabyte of storage and have higher capacities than either RAID or optical.
The bottom line is that for the foreseeable future, optical jukeboxes may continue to occupy a niche between fast but costly disk storage systems and less dependable but cheaper tape subsystems. But the niche will be substantial. J.B. Miles of Pahoa, Hawaii, writes about communications and computers. E-mail him at firstname.lastname@example.org.