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MasterDisk RPS®

 The high reliability storage array with a fully Redundant Power System - RPS.


The Background: "The chain is only as strong as its weakest link"

The disk drives available today have been designed for both high reliability and high performance. Most new disk drives are boasting MTBF ratings in excess of 500,000 hours or more than 57 years. Some are even rated at more than one million hours; almost 115 years. But what good is the perfect disk drive if its power supply fails? The average power supply today has an MTBF of only about 25,000 hours or less than 3 years. Even the most expensive power supplies used in the computer industry today barely exceed 50,000 hours. While your disk drive is not likely to fail over its useful life, its power supply very likely will. To solve this problem, American Digital Systems developed MasterDisk® RPS, the MasterDisk® Redundant Power System.

The Technology

RPS utilizes an independent power supply for each drive in the MasterDisk RPS chassis. The failure of one power supply won't effect the rest of the drives in the RPS storage array. But to further protect the storage system, RPS incorporates an additional power supply; a hot spare; which is online and ready to take over the responsibilities of any other supply in the system should the need arise. RPS uses a high speed switching circuit to immediately remove the defective power supply from its target drive and replace it with the hot spare power supply. The switching time is only 30 billionths of a second and the drive never even knows that a power supply had gone down. An integral microprocessor controlled circuit monitors all power supplies in the array including the hot spare supply and even keeps a history of their performance. When a failure has occurred, the microprocessor sounds the audible warning, flashes the supply failure light, displays a message for the user showing which power supply has failed and exactly how it has failed and even marks the defective power supply.

And if the RPS chassis is in the computer room and you're not, a remote alarm can be wired to the operator's console or a digital pager. All you have to do is go to the rear of the chassis, pull the defective power supply out and replace it. There is no need for tools; no need to turn off the AC power, no need to halt the processor or reboot. In fact, if you replace a defective power supply within one hour of the failure, the MTBF of available power to the disk drives grows from 25,000 hours to more than 1,500,000 hours, more than 170 years.

The Features

The MasterDisk RPS chassis supports all standard SCSI busses including SCSI 1, SCSI 2, Fast SCSI 2, Ultra SCSI and the new Ultra 2 SCSI with differential, single ended or Low Voltage Differential transmission. MasterDisk® RPS can be connected to any SCSI based computer system and most systems which do not use a native SCSI bus. The MasterDisk® RPS chassis can house up to 7 drives, 8 power supplies and a wide variety of performance enhancing features including MasterCache, MasterDisk RAID controllers and MasterDisk® RF-Series DSSI to SCSI protocol converters.

Drive types can include magnetic disk drives, 4mm tape and rewritable optical disk drives. To make the system even easier to use, the drives are mounted to removable modules which can be quickly inserted or removed, even when the system is running - inserted or removed without tools. We've even installed redundant cooling fans and a sophisticated air flow monitoring system which is monitored by the microprocessor.

RAID - For Even More Protection

The hot topic in disk storage systems today is RAID, Redundant Array of Inexpensive Disks. RAID protects your data by storing it across multiple disk drives. Should one disk drive fail, the data can be either copied from the mirrored disk or reconstructed from the remaining disks in the array. It's a great concept and MasterDisk® RPS is ready. The RPS chassis is has all of the necessary provisions for RAID. And the combination of RPS and RAID gives your data the maximum of protection.

The Warranty

American Digital Systems is so sure of its quality, it backs every MasterDisk® RPS storage system with a full five year warranty. That's five years of peace of mind.


Drives per chassis up to 7
Drive types magnetic disk, 4mm tape, rewritable optical disk
Drive form factor 3 ½" half height (1.6") or 1" thick
Bus interface SCSI (SCSI 1), SCSI 2, Fast SCSI 2, Ultra SCSI, Ultra 2 SCSI - can be intermixed, SCSI single ended, Low Voltage Differential or differential - up to 7 independent SCSI buses per chassis
System compatibility All SCSI based systems, servers and workstations and their operating systems including all DEC Alpha, VAX and RISC, all Sun, all SGI, all PC workstations and servers including Windows, NT and Unix, Macintosh, HP, IBM RS6000
RAID compatibility System is fully compatible with all currently available SCSI RAID controllers and supports RAID levels 0, 1, 3, 5 and combinations of those levels - space provided in chassis for RAID hardware
Additional compatibility System provides space and support for additional internal modules such as single-ended to differential converters, RAID controllers, DSSI converters, MasterCache caching modules, etc.
Power system Fully redundant DC power providing available power with an MTBF of 1.6 million hours (> 182 years), one supply per drive plus a redundant supply for the array - up to 8 power supplies per chassis - power supply redundant switch over time < 30 nanoseconds
Drive mounting Drives mounted to removable modules at front of chassis for quick replacement by unskilled personnel - MTTR less than 1 minute
Power supply mounting Power supplies mounted to removable modules at rear of chassis for quick replacement by unskilled personnel - MTTR less than 1 minute
System monitor Microprocessor controlled system monitor for all supply voltages within chassis and proper system cooling - LED display to show system status and fault conditions - audible and visual warning indicators - remote warning indicator
Chassis dimensions

Rack mount - industry standard 19" equipment rack, 5¼" high (3U), 25" deep

Table top mount - 19" wide x 5 ½" high x 25" deep

Floor stand mount - 20 ½" high (including foot assembly) x 25" deep x 5 ¼" wide (8 ½" wide across foot assembly)

Chassis weight 34 pounds (nominal) plus 2.1 pounds per drive (nominal) and 14 ounces per power supply
AC power requirements 90 to 264 VAC, 47 to 63 Hz, 25 Watts per drive typical, 63 Watts per drive maximum
DC power source +5 VDC ± 2% @ 4A maximum, +12 VDC ± 2% @ 3A maximum per drive module
Cooling Redundant 5" dc fans with air flow monitoring circuitry
Controls and indicators

Chassis - LED display status panel, DC OK, Fault, Front Fan failure, Rear Fan failure status lamps, audible warning with acknowledge, remote warning circuit, AC power with indicator

Disk Drive Module - SCSI ID display, SCSI ID selection (0-9 and A-F), drive activity indicator, drive power safety switch

Power Supply Module - Module OK status lamp

Interconnections SCSI or wide SCSI, up to seven busses per chassis, optional non-SCSI busses such as DEC DSSI, remote warning connector

Temperature - 5° to 50° C operating

Temperature - -20° to 75° C storage

Altitude - -1,000 to 20,000 ft operating

Altitude - -1,500 to 60,000 ft transit

Humidity - 5% to 90% non-condensing operating

Preventative maintenance none
MTTR (mean time to repair)

Power supply module replacement - < 1 min

Drive module replacement - < 1 min