Magneto-Optical Storage comes of age

Magneto-Optical Storage comes of age

By Zatni Arbi

JAKARTA (JP): The 5.25" rewritable magneto-optical (MO) disk was a hot, newly-released storage product in 1988. But for four years following its launch its storage capacity remained static; at 650 MB of data. In the last few years there has been a dramatic change, however, and we now have MO disks that hold up to 1.3 Gigabytes of data on two sides (650 MB per side). Some MO disks can even store 2.6 'Gigs'. We now also have the 3.5", 128 MB version of the MO drives and disks.

Pinnacle Micro, from Irvine, California -- one of the major players in MO disk storage -- released its interesting Orray optical disk system last year. Partly following the model of the hard disk-based RAID storage architecture, Orray has four removable 1.3 disks in one casing, allowing you to store up to 5.2 GB with the speed of a hard disk. That was a boon to MO enthusiasts, as this technology had traditionally been known for its slower disk access times and longer disk write times when compared to magnetic hard disks. Unfortunately, at almost US$15,000 per unit, the Orray system was out of many people's reach.

Much less expensive than Orray -- but still expensive for ordinary applications -- are the MO drives from Sony. I was lucky enough to be able to test drive Sony's 5.25" MO drive, the SMO- F521, which carries a Rp 4.5 million price tag.

Magneto optical

I had been searching the mass storage market for a database for my office. To begin with, we wanted to build a simple database to meet the needs of our administrative department. In time, though, we wanted to develop the system into a fully- fledged database, supporting the work of our researchers as well. Given this growth consideration, I set out to find a better alternative to a high-capacity hard disk with a tape backup system -- the traditional means of storage for databases. Definitely, the storage system I was looking for would allow plenty of room for growth.

Among the products available in Glodok, Jakarta, are the double-density MO drives from Sony. The internal drive that I tested looked almost like a regular CD ROM drive, except that it was more than one inch deeper and was much, much heavier because of the complex optical mechanism contained in it. For fear of scratching the sides of the loaned drive, I never tried to slide it into my PC, but it should fit into any 5.25" bay without difficulty. Of course, if you happen to have a mini tower or a slim case, you will probably run into a space problem.

Other MO drives from Sony that are available in Glodok include the 5.25" external and the 3.5" internal (the latter stores a maximum of only 128 MB per disk). The one I tested was an Original Equipment Manufacturer (OEM) version, which means that there is no Sony logo on the front panel. You can find both the unit I tested and its external cousin in the accompanying illustration. The price difference between the Sony brand and an OEM unit is pretty substantial, at about Rp 1 million.

I tested this MO drive with a SCSI-2 board from AdvanSys, i.e., AdvanSCSI Silver Multi-media Kit. I've chosen the ISA bus master version of this SCSI board, as I still don't know whether it will be used on a VL or PCI PC (while the speed is not optimal, the ISA board gives me the freedom to choose the system to install it later on, as it can be used on both VL Bus and PCI motherboards). AdvanSCSI comes with CorelSCSI-2 software and a ribbon cable for internal SCSI devices.

Using the universal Write-Once/Rewritable driver that comes with CorelSCSI, I was able to add the MO drive to my system. I haven't been fully successful in setting up the SCSI subsystem correctly, as Central Point Backup still doesn't recognize it. Nevertheless, the MO drive became Drive D: while my regular CD ROM drive became Drive E:. I was able to write on the MO disk and read from it with no problems.

MO Basics

In an MO drive, the data recording, reading and erasing operations rely on the use of an electromagnetic head, a laser diode, two polarized beam splitters, and two photodetectors -- one for "0"s and the other for "1"s. The recording layer of the disk contains magnetic domains, the orientation of which can be changed during the recording operation with the help of the heat from the laser beam and the application of an electromagnetic field (it's a combination of thermal and magnetic recording mechanisms). When the magnetization is upward, it is a "0"; when it is downward, it is a '1".

During the read operation, the direction of the magnetic field affects the direction of the reflected laser beam, and using the so-called Kerr Effect calculation the read mechanism will determine whether it is reading a "0" or a "1".

Sony claims that the average seek time is 40 ms, and the data transfer rates are 2.0 MB/sec or 1.0 MB/sec, depending on whether the data is stored on the outer or inner ring of the disk platter. Needless to say, this level of performance is still far below an SCSI hard disk, although it is far better than the floppy disk or tape.

MO Cartridges

For the drive, I was also able to test the 1.3 GB cartridge, which you can see in the accompanying illustration, too. The price was about Rp. 400,000 a piece. Actually, each side of this cartridge stores 652 MB of data, and you can flip it to use both sides. The DOS FORMAT command will not work with this cartridge. However, both CorelSCSI's DOSTOOLS and WindowsTOOLS will format it in less than three seconds.

Sony claims that, since it uses the magneto-optical system, the disk can be rewritten a virtually unlimited number of times. As they put it, "the error rate will not change even if the disk is rewritten more than 10 million times".

Test results

Using the simple DOS XCOPY/S command, it took me almost three hours to back up my nearly full 540 MB IDE hard disk to the MO cartridge. Using CorelSCSI Backup utility took almost as long. But this extended backup time could have been the result of a less-than-proper SCSI setup, in addition to the fact that MO drives always take longer to write than to read.

To test whether the MO was still suitable for primary storage purposes, I installed Photoshop 3.0 on the D: drive. When I started the program, it didn't take noticeably longer time to load than when I started it from the hard disk. The reason for this snappy performance is perhaps that Photoshop is a memory- intensive rather than disk-intensive program. Frankly speaking, as I'm a true beginner in Photoshop I don't know how to test the drive to its limits with this top graphics program. Nonetheless, I noticed that it didn't take very long to load the many sample images that came with Photoshop 3.0.

I then tried to run Calligari's TrueSpace, a high-end 3-D animation program, from its backup directory in drive D:. The program still ran acceptably fast, so I think it's safe to conclude that you can run your programs -- if you don't have a better choice -- from an MO drive, albeit perhaps at a 386 performance.

Unfortunately, I didn't have a large database to test the performance of MO. A huge database would have been the best tool for this kind of test, as applications such as this one are much more hard-disk intensive. In general, however, MO disks are considered suitable for applications such as archival storage, document management, image processing, and large-sized databases.

Conclusion

Let's do some straightforward maths here. If we buy an MO drive and a cartridge, both will cost us Rp4.9 million and both will give us a 1.3 GB storage space. That means that the MO system will cost about Rp. 3,750 per MB. That doesn't sound very enticing, given the current price of high-capacity SCSI hard disks, of Rp 1,400 per MB. However, as we add more cartridges, each of which comes at Rp 300 per MB, the MO option becomes more attractive. While the initial investment is hefty, the price per MB storage capacity becomes cheaper as its total size increases.

Add to this expandability the benefits that hard drives don't offer, such as portability, durability (the cartridge is backed by a five-year warranty), longevity (Sony claims it to be at least 15 years), and security (you can easily keep a cartridge containing sensitive data in a safe place) and, depending on your requirements, MO may prove an excellent alternative for mass storage.