Micropolis Raidion™ LT


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Micropolis Raidion LT Modular Desktop Storage Enclosure for 3.5-Inch half-height/"slim line" Hard-Disk Drives

The Micropolis Raidion™ series of storage enclosures consists of modular bricks of high transfer rate digital storage systems, intercoupled multiple digital storage units. The systems can be scaled from smaller stackable desktop or deskside units, which is a common configuration for the "Raidion LT", 7-units tall towers and even large 19" rack based systems for datacenter use. The Raidion SCSI array lineup was introduced in mid 1991.

Raidion LT can be stacked up to seven modules high for convenient desk top use. Each storage module houses a single SCSI drive, its own power supply and a fan. Multiple "towers" with up to 28 modules can be put into an array, with a total storage yield of potentially 47 gigabytes. Drives recommended for single storage modules range from 340MB to 2GB. As each modules has its own PSU, the array has higher redundancy but failing drives are not per-se hot-pluggable, as they are usually daisy-chained and the bus has to be shut down to fix a drive from the array. That said, actual channel and chaining layout of a LT stack of drives is configured by modular cabling of the individual modules. This way one stack of modules may be daisy-chained or may be multiple individual SCSI channels that are just stacked on top of each other.

To customers the system was sometimes marketed as "Speedstack" due to the ease of how modules could be added. Early Systems that were shipped before the "Raidion" product name was established carry the name "MicroDisk LS" on the top lid. On systems tuned for audio-visual workloads, with AV disks, this label was "MicroDisk AV LT". The Raidion LT system, introduced as a simple JBOD enclosure, was usually configured as a software RAID via Micropolis' own RAIDWARE™ Novell extension drivers and connected to a computer system via a SCSI host adapter, like an Adaptec 1502/1505 or 1540 card. Due to how the RAIDWARE software was designed, early versions could only accomodate for Micropolis-built hard-drives - a later software patch removed this limitation. If the software patch can't be applied, it is possible to make drives like the Micropolis 4221, 1991 and similar drives compatible via patching the drives' EEPROM.

Raidion LTX

To satisfy demand for higher availability of on-line storage via redundancy, Micropolis worked on the software RAID JBOD limitation of the "LS" and "LT" systems and introduced, soon after availability of the smaller 3.5" Raidion LT system, an improved version named "Raidion LTX". Raidion LTX is a RAID enclosure with a hardware RAID controller at its base, controlling all drives stacked on top of it and presenting the array of drives as one single volume to the host computer system. Internally Micropolis used codename "Gandiva" for this hardware RAID Raidion version and the Gandiva codename can be found in module product numbers and is printed on the hardware controller PCBA. Many Micropolis products carry the name of antique weaponry and "Gandiva" is no exception, being a divine bow mentioned in the texts of Hinduism. It is owned by Arjuna, one of the Pandavas from the epic Mahabharata.

The Raidion LTX Gandiva hardware RAID controller implements four SCSI channels with support for 7 drives per channel. The hardware RAID made the "LT" system truly hot-plug and improved fault-tolerance dramatically. Internally, between modules, the SCSI bus is 50-pin for 50-pin SCSI disks while the hardware RAID controller exposes a 68-pin SCSI interface with SCSI ID towards the host computer system.

As the LTX systems could be built into large assemblies and datacenter operators increasingly migrated towards the 19"-rack system layout, Micropolis presented a 19" compatible module shelf for drive modules and a separated-out hardware RAID controller. The "RT Subrack Assembly", sometimes nicknamed the "8 car garage", fitted 8 LM drive modules vertically into one shelf for eight 3.5" drives. The "RS Subrack Assembly" divided the 19" wide footprint into three "drawers" (sometimes "3 car garage") and fitted 5.25" hard disks - as the rack equivalent of using Raidion LS 5.25" deskside drive modules. A similarly rack-fitted 19" hardware RAID controller, Micropolis RTX or RX, connected the array and made the drive shelves available to the connected host computer.

Both version of the Gandiva Raidion hardware controller, rack and desktop, feature a built-in LCD/Keypad interface. This way, users can configure and manage the Raidion array via the GUI software or the on-device display keypad menu. Additionally, a RS232 serial interface can be utilized to maintain the controller.

During the introduction of the Raidion storage arrays, Micropolis began to separate this business into what would become StreamLogic. Thus, some Raidion components carry the StreamLogic brand, the Micropolis brand or both. Later, when businesses were further unspun, Raidion storage arrays were marketed by Raidion Systems for some time.

Common compatible SCSI controllers:
Adaptec AHA-1502 (ISA, one port)
Adaptec AHA-1505 (ISA, two ports)
Adaptec AHA-1540 (ISA)
Adaptec AHA-1640 (PS/2 Microchannel)
Adaptec AHA-1740 (EISA)
Adaptec AHA-2740 (EISA)


  • LM 1050 - 1050MB capacity, 3.5-inch form-factor (desktop, plastic enclosure plus drive chasssis)
  • LM 1760 - 1760MB capacity, 3.5-inch form-factor (desktop, plastic enclosure plus drive chasssis)
  • SMXXXX-SERIES - Drive Chassis (desktop, P/N SM9100-01-4)
  • RSO-XXX - Drive Module, 5.25" drive drawer (rack, P/N 200340-01-6)
  • RSO-XXX - RTX Drive Module, (rack, P/N DM0031-02-0)
  • RX-XXX - RTX Hardware Controller (rack, P/N GAN031-01-7)