Tape Path

Guiding the tape through the tape path and across the read/write head is one of the key technologies in any tape drive. Limiting the tape wear (especially limiting edge damage to the tape) is becoming more important. To increase capacities tapes are getting longer and therefore thinner. The tape path mechanics must be designed to gently guide this thinner and more fragile tape.

Pressurized air bearings

Traditionally, high-end tape drives used pressurized air bearings ("hydro static bearings"). Recent advances in this technology include low-flow bearings.

The requirement for low cost, and advances in other technologies, have made pressurized bearings obsolete.

Hydrodynamic bearings

hydrodynamic bearings

The tape creates a thin air film as it moves over hydrodynamic bearings. Controlling the stability of this air film is crucial. When tape stops it comes in contact with the bearings. Tape will stick to the bearings in hot and humid environments if the bearing is not designed very carefully.

MEII has designed 3 generations of tape drives with hydrodynamic bearings.

Mathematical tools

Mathematical analysis with the latest available tools is an integral part of our design process. Our models have been developed and refined during the development of 4 tape drive generations. They can accurately predict important parameters such as movement of tape, stress on tape, resonant frequencies, etc. The use of these tools ensures high quality designs that work the first time.

tape path analysis

See demonstration videos of one of the mathematical tools used to analyze the tape path.

Read Write

Requirements for the next generation tape drives include higher linear recording densities, greater data transfer rates, lower power consumption, smaller physical size, and lower cost. All these constraints require unique design innovations that are one of MEII's strongest assets.

Higher linear recording densities translate into smaller tape read-back signals and the potential for higher data error rates. MEII's expertise in this area ensures peak performance as data densities increase. It is through many years of experienced circuit design coupled with heavy analytical integration that ensure low error rates which result in a product which is highly reliable.

Data transfer rates continually increase to keep up with the user's requirement to backup large amounts of data in the shortest period of time. Native (without compression) sustained data rates exceed 20 MB/s in new generation tape drives. It is here that as analog data frequencies increase, Read/Write design for low noise and high signal integrity is of utmost importance.

The recording quality of tapes change as tapes are subjected to harsh environmental conditions and extended periods of storage time. MEII has developed advanced, mathematical models to ensure that our circuits can accurately recover the stored data, even from marginal tapes.

Data transfer rates are constantly increasing to keep up with the requirement to backup large amounts of data in a short time. Native (without compression), sustained data rates exceed 20 MB/s in new tape drives. The tape drives are getting smaller at the same time. This requires unique designs and custom components that can handle high speed signals in close proximitry to each other.


Increasingly thinner tape, narrower track width, and increased linear density all require precise servo control. Tape winding tension and tape speed need to be controlled within tight tolerances.

To keep pace with increasingly faster channels, the data rates to and from tape also must increase. Increased data rates require fast tape speeds, so that tape speeds of 4m/s are now common. Some tape drives scheduled to be available within the year will have tape speeds above 6m/s.

Most tape systems have servo tracks on tape or other means that indicate the precise position of the tape relative to the head. Minute movements of the tape are detected and fed to a positioning system that moves the head to compensate for such tape movements. This system also automatically compensates for any height differences between tape drives. Interchange problems due to differences in head height between tape drives will now be a problem of the past.

MEII has developed models to predict the behavior of the servo systems.


In order to maintain a high level of customer satisfaction, efficient controller design requires the coordinated efforts of hardware and software professionals. Well-integrated tape drive design requires experience and resources in the fields of interface design, data compression technology, error-correction techniques, buffer memory architecture and tape-format-specific coding and decoding methods. A few words about each area of expertise follow.

Buffer Memory Architecture

Buffer memories are used to temporarily store user data being transferred to or from tape. Buffer memories, essentially large reservoirs of data, are a valuable resource because they provide speed-matching capability between the interface and the drive. Without a buffer a slow user interface (i.e. SCSI 5Mbytes/sec) retrieving data from a fast drive (12Mbyes/sec) could force the drive into a seesawing, start/stop motion. This motion could result in an both an overall reduction in the data throughput rate and in excessive wear on the tape head. Adding a buffer of sufficient size and performance allows the drive to stockpile the data and produces far fewer start/stop motions. A corresponding scenario would occur if the host interface were faster than the tape drive.

MEII's memory architectures provide peak performance in several ways. Like a super highway, the data path width to/from the buffer widens out, allowing large amounts of data to be transferred in a small amount of time. This architecture translates to increased bandwidth. The designs are fully pipelined with FIFOs (First-In-First-Out memory elements) incorporated in the input and output structures to the memory arrays. FIFOs further accelerate the movement of data. An off-the-shelf DMA controller is incapable of providing the performance which is required of state-of-the-art tape drive systems. Therefore, most of the designs developed by MEII incorporate custom DMA controllers that can adequately handle the data flow.


The key to developing lower cost tape drives is integration. In order to achieve high levels of compression MEII is fully experienced in FPGA architecture (Field Programmable Gate Array) and in custom ASIC design (Application Specific Integrated Circuit). FPGAs provide maximum flexibility and allow the product to rapidly adapt to changes in today's storage needs. ASICs minimize the product cost and maximize the performance. MEII uses advanced design techniques involving HDL (Hardware Description Language) language syntax (Verilog) in association with vendor-supplied gate synthesis tools. These techniques enhance error-free hardware implementations. The greatest benefit of HDL design is that it allows re-targeting the hardware implementation in response to newer device technology as it becomes available.

A Final Word

There was a day when the mention of the word "tape drive" was synonymous with "archaic", "old-tech", and "unreliable". MEII is working hard to replace those tired words and is dedicated to developing superlative tape drives at cost-effective prices. When considering your next tape drive project, contact MEII .