4. Introduction

The Antares 5070 is a high performance, versatile, yet relatively inexpensive host based RAID controller. Its embedded operating system (K9 kernel) is modelled on the Plan 9 operating system whose design is discussed in several papers from AT&T (see the "Further Reading" section). K9 is a kernel targeted at embedded controllers of small to medium complexity (e.g. ISDN-ethernet bridges, RAID controllers, etc). It supports multiple lightweight processes (i.e. without memory management) on a single CPU with a non-pre-emptive scheduler. Device driver architecture is based on Plan 9 (and Unix SVR4) streams. Concurrency control mechanisms include semaphores and signals.

The 5070 has three single ended ultra 1 SCSI channels and two onboard serial interfaces one of which provides command line access via a connected serial terminal or modem. The other is used to upgrade the firmware. The command line is robust, implementing many of the essential Unix commands (e.g. dd, ls, cat, etc.) and a scaled down Bourne shell for scripting. The Unix command set is augmented with RAID specific configuration commands and scripts. In addition to the command line interface an ASCII text based GUI is provided to permit easy configuration of level 0, 1, 3, 4, and 5 RAIDs.

4.1 5070 Main Features

• RAID levels 0, 1, 3, 4, and 5 are supported.
• Text based GUI for easy configuration for all supported RAID levels.
• A Multidisk RAID volume appears as an individual SCSI drive to the operating system and can be managed with the standard utilities (fdisk, mkfs, fsck,etc.). RAID Volumes may be assigned to different SCSI IDs or the same SCSI IDs but different LUNs.
• No special RAID drivers required for the host operating system.
• Multiple RAID volumes of different levels can be mixed among the drives forming the physical plant. For example in a hypothetical drive plant consisting of 9 drives:
  • 2 drives form a level 3 RAID assigned to SCSI ID 5, LUN 0
  • 2 drives form a level 0 RAID assigned to SCSI ID 5, LUN 1
  • 5 drives form a level 5 RAID assigned to SCSI ID 6, LUN 0
• Three single ended SCSI channels which can accommodate 6 drives each (18 drives total).
• Two serial interfaces. The first permits configuration/control/monitoring of the RAID from a local serial terminal. The second serial port is used to upload new programming into the 5070 (using PPP and TFTP).
• Robust Unix-like command line and NVRAM based file system.
• Configurable ASCII SCSI communication channel for passing commands to the 5070's command line interpreter. Allows programming running on host OS to directly configure/control/monitor all parameters of the 5070.