History (1994): First Optical Array From Pinnacle Micro

Some, and not only us, are usually careful when it comes to reading announcements from Pinnacle Micro (Irvine, CA), an integrator and distributor of optical products for PC environment.

Concerning one of its M-O drives, we still have in mind an access time spec that was so low that more than one of its competitors hit the roof and probably more than one user was deceived.

The expression of ‘Optical HDD’ often used by the company, for its M-O drives, is a great marketing invention, but remains misleading.

But we must admit that the Californian company had nevertheless some great new products, like for instance its portable 3.5-inch M-O drive, a bit expensive, but cleverly designed, or its low-price CD-WORM device.

The Orray, its new product, is interesting, but let’s keep our eyes opened to detect its qualities but also its flaws. An array, not a RAID, Pinnacle Micro, as it unveiled the Orray Optical Disk System, has developed what we believe to be the first real optical disk array subsystem, which and this is an important point, doesn’t mean a RAID, whatever level it could be.

In fact, Pinnacle doesn’t depict Orray as a RAID, but dares a very hasty comparison with a HDD drive. It’s not one or the other, it’s a subsystem including a tower of 4 stacked drives. Units holding 5.25-inch M-O drives each with a capacity of 650MB per side, this means an announced total capacity of 5.2GB. But for the user, it’s only 2.6GGB on-line, since he has to turn over each disk by hand to get the double. However, the removability of the media offers an unlimited capacity. These 4 drives are operated by a controller, the real pioneering idea of the subsystem, connectable via a Fast SCSl-2 interface (10MB/s) to a computer which looks at it all like a single device.

Reading and writing independently and simultaneously on 4 media
This controller, for which the multi-channel architecture has been patented, can effectively manage each one of the 4 drives separately, i.e. read and write independently and simultaneously any one of the 4 media, with its 4 parallel asynchronous disk data channels.

But this doesn’t mean data stripping or RAID-0. Data is not stripped to be written in parallel, all the less as the drives are not synchronized. But, on account of a large cache, that can reach 64MB of RAM, and a clever organization managed by the controller, the real transfer rate can be 4x the one of a single drive, which means in the best case close to 8MB/s with units spinning at 4,500 rpm.

This could be, for instance, to read video recordings in a sequence. Writing on an M-O disk takes at least 2 rotations of the disk, which divides here the transfer rate at least by 2.

The Orray is not fault-tolerant. There is no parity data writing. But this doesn’t matter because life (over 10 years) and reliability of M-O disks are higher than on any magnetic disk. The first ones have no chances of being damaged by the crash of a laser head. But there is the risk of a drive failure. The subsystem’s MTBF is bound to be 4x lower than that of a drive.

On the Orray, the controller has huge tasks that request powerful processor level. That’s why it has an Intel i960 processor at 100MHz, and additionally four 25MHz Intel 80188 processors, one for each drive.

Four modes
Pinnacle offers the possibility of working in 4 different modes on the Orray: streaming and transaction, standard and ‘Orray’ modes. The controller automatically detects these modes and configures the system depending upon the media inserted.
– Streaming mode is typical of audio/video applications. In this case, Orray uses large cache segment sizes and bursts data to/from SCSI and to/from media in large blocks.
– In transaction mode for network server or database applications where many different regions of the disks are accessed frequently, the system divides the cache into smaller segment sizes so that, with read-ahead and write behind caching, as much data as possible can be accessed without having to access the media.
– In standard mode, the system will appear as a single SCSI ID with SCSI logical units attached to each drive. It provides a means of assigning several standard devices to a single SCSI ID. It’s not the most inventive mode but this provides compatibility with current standardized media. And here, any kind of ISO/ECMA media can be inserted.
– It’s not the same for the ‘Orray’mode, the most interesting one, that requires buying from Pinnacle, and only from Pinnacle, a special pack of 4 disks that cost twice as much as if they were bought separately. Each cartridge has a different color so it can be recognized and placed in the appropriate drive. The pack is assigned a unique number at formatting to denote all disks belonging to the pack, and each disk is sequentially numbered according to each drive. In this mode, the subsystem appears as a single SCSI direct access device with a 2.6GB capacity online. At the interface between the master controller that splits the R/W orders and distributes them to four 4 controllers (one per drive), data is here multiplexed to get the maximum speed, 4x the individual transfer rate of each drive in the best case. The patent technology allows all active disk surface to transfer data simultaneously without requiring the data from a given surface to be synchronized to the other disk surfaces, allowing independent seek, read, erase, write, error recovery operation without preventing other surfaces from completing their electronics are dedicated to each surface, while surface one’s data is being transferred, the other 3 surfaces’ data is being buffered.

When all this in a jukebox?
For the price of the Orray, $14,995, at the end you finally only get 2.6GB on-line ($5.75/MB)or double if you turn the disk around ($2.9/MB) with higher performances than those of a HDD drive only in some cases. This can make the customer hesitant. But, by turning over or changing the disk by hand, the capacity is limitless.

In our opinion, the Orray could undeniably offer an enhancement if the disk could be turned over and loaded automatically, i.e. if it was designed like a jukebox with several dozen disks, 4 drives, with a robot changing the 4 disks at once. Then the amazing Orray mode would have all its meaning, mainly for audio/video and especially video on demand applications.

For the future, we can imagine the possibility of making real optical RAIDS, not in RAID-1 (mirroring), in RAID-3 or 5 (fault tolerance doesn’t seem to be an absolute necessity on optical disks), but rather a RAI-0 (data stripping only) that wouldn’t improve access time but multiply in every case the transfer rate by the number of synchronized drives, mainly in writing mode, quite slow on M-O disks.

This article is an abstract of news published on the former paper version of Computer data Storage Newsletter on issue 77, published on June 1994.

Note: This technology didn’t succeed and optical array never was developed by another company.