Magneto-Optical Storage comes of age<\/p>\n
By Zatni Arbi<\/p>\n
JAKARTA (JP): The 5.25\" rewritable magneto-optical (MO) disk
\nwas a hot, newly-released storage product in 1988. But for four
\nyears following its launch its storage capacity remained static;
\nat 650 MB of data. In the last few years there has been a
\ndramatic change, however, and we now have MO disks that hold up
\nto 1.3 Gigabytes of data on two sides (650 MB per side). Some MO
\ndisks can even store 2.6 'Gigs'. We now also have the 3.5\", 128
\nMB version of the MO drives and disks.<\/p>\n
Pinnacle Micro, from Irvine, California -- one of the major
\nplayers in MO disk storage -- released its interesting Orray
\noptical disk system last year. Partly following the model of the
\nhard disk-based RAID storage architecture, Orray has four
\nremovable 1.3 disks in one casing, allowing you to store up to
\n5.2 GB with the speed of a hard disk. That was a boon to MO
\nenthusiasts, as this technology had traditionally been known for
\nits slower disk access times and longer disk write times when
\ncompared to magnetic hard disks. Unfortunately, at almost
\nUS$15,000 per unit, the Orray system was out of many people's
\nreach.<\/p>\n
Much less expensive than Orray -- but still expensive for
\nordinary applications -- are the MO drives from Sony. I was lucky
\nenough to be able to test drive Sony's 5.25\" MO drive, the SMO-
\nF521, which carries a Rp 4.5 million price tag.<\/p>\n
Magneto optical<\/p>\n
I had been searching the mass storage market for a database
\nfor my office. To begin with, we wanted to build a simple
\ndatabase to meet the needs of our administrative department. In
\ntime, though, we wanted to develop the system into a fully-
\nfledged database, supporting the work of our researchers as well.
\nGiven this growth consideration, I set out to find a better
\nalternative to a high-capacity hard disk with a tape backup
\nsystem -- the traditional means of storage for databases.
\nDefinitely, the storage system I was looking for would allow
\nplenty of room for growth.<\/p>\n
Among the products available in Glodok, Jakarta, are the
\ndouble-density MO drives from Sony. The internal drive that I
\ntested looked almost like a regular CD ROM drive, except that it
\nwas more than one inch deeper and was much, much heavier because
\nof the complex optical mechanism contained in it. For fear of
\nscratching the sides of the loaned drive, I never tried to slide
\nit into my PC, but it should fit into any 5.25\" bay without
\ndifficulty. Of course, if you happen to have a mini tower or a
\nslim case, you will probably run into a space problem.<\/p>\n
Other MO drives from Sony that are available in Glodok include
\nthe 5.25\" external and the 3.5\" internal (the latter stores a
\nmaximum of only 128 MB per disk). The one I tested was an
\nOriginal Equipment Manufacturer (OEM) version, which means that
\nthere is no Sony logo on the front panel. You can find both the
\nunit I tested and its external cousin in the accompanying
\nillustration. The price difference between the Sony brand and an
\nOEM unit is pretty substantial, at about Rp 1 million.<\/p>\n
I tested this MO drive with a SCSI-2 board from AdvanSys,
\ni.e., AdvanSCSI Silver Multi-media Kit. I've chosen the ISA bus
\nmaster version of this SCSI board, as I still don't know whether
\nit will be used on a VL or PCI PC (while the speed is not
\noptimal, the ISA board gives me the freedom to choose the system
\nto install it later on, as it can be used on both VL Bus and PCI
\nmotherboards). AdvanSCSI comes with CorelSCSI-2 software and a
\nribbon cable for internal SCSI devices.<\/p>\n
Using the universal Write-Once\/Rewritable driver that comes
\nwith CorelSCSI, I was able to add the MO drive to my system. I
\nhaven't been fully successful in setting up the SCSI subsystem
\ncorrectly, as Central Point Backup still doesn't recognize it.
\nNevertheless, the MO drive became Drive D: while my regular CD
\nROM drive became Drive E:. I was able to write on the MO disk and
\nread from it with no problems.<\/p>\n
MO Basics<\/p>\n
In an MO drive, the data recording, reading and erasing
\noperations rely on the use of an electromagnetic head, a laser
\ndiode, two polarized beam splitters, and two photodetectors --
\none for \"0\"s and the other for \"1\"s. The recording layer of the
\ndisk contains magnetic domains, the orientation of which can be
\nchanged during the recording operation with the help of the heat
\nfrom the laser beam and the application of an electromagnetic
\nfield (it's a combination of thermal and magnetic recording
\nmechanisms). When the magnetization is upward, it is a \"0\"; when
\nit is downward, it is a '1\".<\/p>\n
During the read operation, the direction of the magnetic field
\naffects the direction of the reflected laser beam, and using the
\nso-called Kerr Effect calculation the read mechanism will
\ndetermine whether it is reading a \"0\" or a \"1\".<\/p>\n
Sony claims that the average seek time is 40 ms, and the data
\ntransfer rates are 2.0 MB\/sec or 1.0 MB\/sec, depending on whether
\nthe data is stored on the outer or inner ring of the disk
\nplatter. Needless to say, this level of performance is still far
\nbelow an SCSI hard disk, although it is far better than the
\nfloppy disk or tape.<\/p>\n
MO Cartridges<\/p>\n
For the drive, I was also able to test the 1.3 GB cartridge,
\nwhich you can see in the accompanying illustration, too. The
\nprice was about Rp. 400,000 a piece. Actually, each side of this
\ncartridge stores 652 MB of data, and you can flip it to use both
\nsides. The DOS FORMAT command will not work with this cartridge.
\nHowever, both CorelSCSI's DOSTOOLS and WindowsTOOLS will format
\nit in less than three seconds.<\/p>\n
Sony claims that, since it uses the magneto-optical system,
\nthe disk can be rewritten a virtually unlimited number of times.
\nAs they put it, \"the error rate will not change even if the disk
\nis rewritten more than 10 million times\".<\/p>\n
Test results<\/p>\n
Using the simple DOS XCOPY\/S command, it took me almost three
\nhours to back up my nearly full 540 MB IDE hard disk to the MO
\ncartridge. Using CorelSCSI Backup utility took almost as long.
\nBut this extended backup time could have been the result of a
\nless-than-proper SCSI setup, in addition to the fact that MO
\ndrives always take longer to write than to read.<\/p>\n
To test whether the MO was still suitable for primary storage
\npurposes, I installed Photoshop 3.0 on the D: drive. When I
\nstarted the program, it didn't take noticeably longer time to
\nload than when I started it from the hard disk. The reason for
\nthis snappy performance is perhaps that Photoshop is a memory-
\nintensive rather than disk-intensive program. Frankly speaking,
\nas I'm a true beginner in Photoshop I don't know how to test the
\ndrive to its limits with this top graphics program. Nonetheless,
\nI noticed that it didn't take very long to load the many sample
\nimages that came with Photoshop 3.0.<\/p>\n
I then tried to run Calligari's TrueSpace, a high-end 3-D
\nanimation program, from its backup directory in drive D:. The
\nprogram still ran acceptably fast, so I think it's safe to
\nconclude that you can run your programs -- if you don't have a
\nbetter choice -- from an MO drive, albeit perhaps at a 386
\nperformance.<\/p>\n
Unfortunately, I didn't have a large database to test the
\nperformance of MO. A huge database would have been the best tool
\nfor this kind of test, as applications such as this one are much
\nmore hard-disk intensive. In general, however, MO disks are
\nconsidered suitable for applications such as archival storage,
\ndocument management, image processing, and large-sized databases.<\/p>\n
Conclusion<\/p>\n
Let's do some straightforward maths here. If we buy an MO
\ndrive and a cartridge, both will cost us Rp4.9 million and both
\nwill give us a 1.3 GB storage space. That means that the MO
\nsystem will cost about Rp. 3,750 per MB. That doesn't sound very
\nenticing, given the current price of high-capacity SCSI hard
\ndisks, of Rp 1,400 per MB. However, as we add more cartridges,
\neach of which comes at Rp 300 per MB, the MO option becomes more
\nattractive. While the initial investment is hefty, the price per
\nMB storage capacity becomes cheaper as its total size increases.<\/p>\n
Add to this expandability the benefits that hard drives don't
\noffer, such as portability, durability (the cartridge is backed
\nby a five-year warranty), longevity (Sony claims it to be at
\nleast 15 years), and security (you can easily keep a cartridge
\ncontaining sensitive data in a safe place) and, depending on your
\nrequirements, MO may prove an excellent alternative for mass
\nstorage.<\/p>",
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