Stratus Continuum
Thanks to Ti Kan (2004) for the input.
Stratus Technologies produced a line of Ultra High Availability Fault Tolerant
PA-RISC servers, called Continuum, in the 1990s.
Continuum were based on different PA-RISC processors and sold as Continuum 400, 600 and 1200 series between 1995 and 2004.
These fault tolerant Stratus server feature a great deal of redundancy, with up to four CPUs to form one single logical processor.
Before PA-RISC, Stratus used different architectures – Stratus/32, XA400 and XA2000 from the 1980s used Motorola 68000s CPUs and Stratus XA/R from the early-1990s used Intel i860 processors, a RISC/VLIW design.
PA-RISC-powered Continuum were phased out by Stratus in the mid-2000s in favor of Intel-based systems, Xeon Pentium 4 ftServer V Series..
| System | Processor | Year | Base price |
|---|---|---|---|
| Continuum 412 | L1/P2 PA-7100 96MHz PA-RISC 32-bit | 1996 | $66,000 |
| Continuum 418 | L1/P4 PA-8000 180MHz PA-RISC 64-bit | 1996-97 | $140,500 |
| Continuum 428 | L2/P8 PA-8000 180MHz PA-RISC 64-bit | 1996-97 | $240,500 |
| Continuum 618 | L1/P4 PA-8000 180MHz PA-RISC 64-bit | 1996-97 | $274,000 |
| Continuum 628 | L2/P8 PA-8000 180MHz PA-RISC 64-bit | 1996-97 | $424,000 |
| Continuum 1218 | L1/P4 PA-8000 180MHz PA-RISC 64-bit | 1996-97 | $499,000 |
| Continuum 1228 | L2/P8 PA-8000 180MHz PA-RISC 64-bit | 1996-97 | $649,000 |
Prices are only basic server configuration
from HP Professional in 1999.
Continuum 400
The Continuum 400 series has the same CPU/memory architecture as the 600/1200, but the I/O bus is different. Instead of a Golf bus, it has an X bus that connects each CPU/memory module to a pair of PCI bridge boards. All I/O connectivity is via PCI cards.
There are two PCI bays of 7 slots each, connected downstream from the PCI bridge boards. Each bay has a dual channel SCSI adapter on it as standard equipment. These are also cross-wired and dual-initiated much in the same way as the SCSI ports on the 600/1200 systems.
Continuum 400s were also typically shipped with a pair of Ethernet adapter cards. The PCI bridge boards also each contains a removable PCMCIA flash memory card. This is used as the boot device. FTX puts the bootloader as well as the UNIX kernel on there, whereas HP-UX only uses it for the bootloader.
The PCI bay doors control the power the the PCI slots. Once opened, all slots in that bay are powered off to facilitate removal and insertion of cards. The system continues to run on cards in the other bay. An interlock mechanism prevents both bay doors from being opened at the same time.
Two chassis versions were available, one a short form-factor AC-powered, the other a tall CO central office version with a choice of AC or DC power.
The Continuum 400 supported mainly Stratus-modified HP-UX as operating systems, with Stratus own FTX Unix only sold exceptionally.
Continuum 600 and 1200
The Continuum 600 and 1200 series are similar designs but with different chassis configuration. The 600 has six slots for the main Golf bus, and the rest of the space is filled with I/O card cages meant for secondary I/O boards. The 1200 has twelve slots for the main bus which occupies the entire width of the chassis. Secondary I/O boards go into a separate chassis.
Both models have space for two rows of cooling fans on the top, and two rows of disk drives on the bottom and also either a QIC or DAT tape drive or CDROM drive. The redundant power supplies with built-in UPS resides at the very bottom.
The main Golf bus is the main interconnect between the big
boards:
- G7xx: CPU and memory boards
- K450: 4-channel HVD fast wide SCSI and Ethernet adapter
- K460: 4-channel HVD fast wide SCSI and Ethernet adapter
- K470:
carrier board
for PMC PCI-mezzanine daughter cards - K600: Adapter to the secondary I/O card cages
On the 600 chassis, the six slots consists of two for the pair or
CPU/memory boards, and four more slots for two pairs of big
boards.
On the 1200 chassis, there are slots for two pairs of CPU/memory boards
and four pairs of big boards.
In addition the 600/1200 main chassis also has a pair of Console Controller
cards which provides the RS232 console terminal and RSN modem connectivity.
This controller also has a command mode that allows the operator to type
commands on the console to reset the system, power down, power up, etc.
It runs on housekeeping power
that is independent of the rest of the
system. The Console controller also contains some environmental monitoring
circuitry that checks the chassis internal temperature and will increase
the cooling fan speed if necessary.
The secondary I/O chassis can be used to plug in a wide array of I/O boards, all Stratus proprietary. These boards are also used on the XA/R line. FTX supported many of the communications boards like ISDN, serial, parallel, X.25, and all sorts of other comm boards. HP-UX did not support many of those, if any. VOS also supported disk and tape I/O through this.
Continuum 600 and 1200 were geared towards the VOS transactional operating system from Stratus, with FTX Unix offered only exceptionally.
Processors and architecture
Each logical processor is physically two pairs of actual CPUs, that
means four physical CPU chips per single logical one.
Each pair is located on a separate FRU. All processors run lock-stepped,
they do exactly the same thing at the same time. Comparator
logic between each two physical CPU pair monitors for discrepancies.
If any physical CPU glitches or does something different, the comparator
logic will detect the error and take that pair of CPUs offline, while
the system continues to run on the other pair. There is no failover
time.
On multi-processor boards, each FRU contains multiple pairs
of the logical processor halves.
The memory is self-checking and ECC corrected. If an uncorrectable error occurs, the FRU in which the memory is located will also be taken offline.
The big I/O boards are also self-checking and contain a pair of everything. However, with the exception of the K600 they do not run lock-stepped to the twin FRU. For example on the K450/K460 boards, each of the SCSI host adapters is connected via the backplane into the same SCSI bus on the partner board, but each board’s controller occupies a different SCSI target ID.
Only one controller is normally active, but when a failure occurs on the active board, all I/O is switched to the other controller. For the Ethernet ports on that board, they can be wired up to the same network or to different networks, and a software RNI redundant network interface layer provides transparent switching. All disks are mirrored.
System Table
| System | CPU | Logical Physical |
Cache per CPU |
RAM max |
Expansion max |
Storage max |
I/O max |
OS |
|---|---|---|---|---|---|---|---|---|
| 412 | PA‑7100 96 MHz |
L1/P2 | 512 KB | 2 GB | 12 PCI | 14 drives 4 CD-ROMs 4 tape |
16 100Mbit 8 T1/E1 64 Async 64 RS232 32 X.21 32 V.35 |
HP-UX, FTX |
| 415 | PA‑7100 96 MHz |
L1/P2 | 2 MB | 2 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 418 | PA-8000 180 MHz |
L1/P4 | 2 MB | 8 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 419 | PA‑8500 360 MHz |
L1/P4 | 1.5 MB | 8 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 422 | PA‑7100 96 MHz |
L2/P4 | 512 KB | 2 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 425 | PA‑7100 96 MHz |
L2/P4 | 2 MB | 2 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 428 | PA-8000 180 MHz |
L2/P8 | 2 MB | 8 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 429 | PA-8500 360 MHz |
L2/P8 | 1.5 MB | 8 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 439 | PA-8600 480 MHz |
L1/P4 | 1.5 MB | 8 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 449 | PA-8600 480 MHz |
L2/P8 | 1.5 MB | 8 GB | 12 PCI | – " – | – " – | HP-UX, FTX |
| 610S | PA-7100 72 MHz |
L1/P4 | 512 KB | 128 MB | 6 slots | VOS, FTX | ||
| 610 | PA-7100 72 MHz |
L1/P4 | 512 KB | 512 MB | 6 slots | VOS, FTX | ||
| 615S | PA-7100 96 MHz |
L1/P4 | 2 MB | 128 MB | 6 slots | VOS, FTX | ||
| 615 | PA-7100 96 MHz |
L1/P4 | 2 MB | 1 GB | 6 slots | VOS, FTX | ||
| 616S | PA-8500 360 MHz |
L1/P4 | 1.5 MB | 0.5 GB | 6 slots | VOS, FTX | ||
| 616 | PA-8500 360 MHz |
L1/P4 | 1.5 MB | 2 GB | 6 PCI 2 Stratus 28 I/O |
L47/P94 disks 4 tape |
10 100Mbit 8 T1/E1 8 TR 4 FDDI 448 Async 112 RS232 28 X.21 56 V.35 |
VOS, FTX |
| 618 | PA-8000 180 MHz |
L1/P4 | 2 MB | 3 GB | 6 slots | VOS, FTX | ||
| 619 | PA-8500 380 MHz |
L1/P4 | 1.5 MB | 4 GB | 6 slots | VOS, FTX | ||
| 620 | PA-7100 72 MHz |
L2/P8 | 512 KB | 512 MB | 6 slots | VOS, FTX | ||
| 625 | PA-7100 96 MHz |
L2/P8 | 2 MB | 2 GB | 6 slots | VOS, FTX | ||
| 628 | PA-8000 180 MHz |
L2/P8 | 2 MB | 3 GB | 6 slots | VOS, FTX | ||
| 629 | PA-8500 380 MHz |
L2/P8 | 1.5 MB | 4 GB | 6 slots | VOS, FTX | ||
| 651-2 | PA-8600 480 MHz (552 MHz?) |
L1/P4 | 1.5 MB | 4 GB | 6 PCI 2 Stratus 28 I/O |
L47/P94 disks 4 tape |
10 100Mbit 8 T1/E1 8 TR 4 FDDI 448 Async 112 RS232 28 X.21 56 V.35 |
VOS, FTX |
| 652-2 | PA-8600 480 MHz (552 MHz?) |
L2/P8 | 1.5 MB | 4 GB | 6 PCI 2 Stratus 28 I/O |
– " – | – " – | VOS, FTX |
| 1210 | PA-7100 72 MHz |
L1/P4 | 512 KB | ? | 12 slots | VOS, FTX | ||
| 1215 | PA-7100 96 MHz |
L1/P4 | 2 MB | ? | 12 slots | VOS, FTX | ||
| 1218 | PA-8000 180 MHz |
L1/P4 | 2 MB | 3 GB | 12 slots | VOS, FTX | ||
| 1219 | PA-8500 380 MHz |
L1/P4 | 1.5 MB | 4 GB | 12 slots | VOS, FTX | ||
| 1220 | PA-7100 72 MHz |
L2/P8 | 512 KB | 512 MB | 12 slots | VOS, FTX | ||
| 1225 | PA-7100 96 MHz |
L2/P8 | 2 MB | 2 GB | 12 slots | VOS, FTX | ||
| 1228 | PA-8000 180 MHz |
L2/P8 | 2 MB | 3 GB | 12 slots | VOS, FTX | ||
| 1229 | PA-8500 380 MHz |
L2/P8 | 1.5 MB | 4 GB | 12 slots | VOS, FTX | ||
| 1245 | PA-7100 96 MHz |
L4/P16 | 2 MB | 2 GB | 12 slots | VOS, FTX | ||
| 1251-2 | PA-8600 480 MHz (552 MHz?) |
L1/P4 | 1.5 MB | 4 GB | 18 PCI 6 Stratus 84 I/O |
L95/P190 disks 4 tape |
18 100Mbit 8 T1/E1 24 TR 8 FDDI 448 Async 112 RS232 84 X.21 168 V.35 |
VOS, FTX |
| 1252-2 | PA-8600 480 MHz (552 MHz?) |
L2/P8 | 1.5 MB | 4 GB | 18 PCI 6 Stratus 84 I/O |
– " – | – " – | VOS, FTX |
- Logical/Physical CPUs:
L
andP
denote Logical and Physical devices — logical CPUs are made up of two pairs of CPUs each (i.e., 2×2) - Storage:
L
andP
denote Logical and Physical devices — logical disk drives are formed from physical devices via RAID sets - I/O: Maximum number of I/O devices supported (not necessarily always configured with this number); notably the devices are also redundant
Operating systems
- Stratus FTX, Stratus System V Unix (on Continuum 400)
- HP-UX 11.00, modified by Convex (on Continuum 400)
- Stratus VOS, Stratus transaction processing (on Continuum 600/1200)
Documentation
- HP-UX Continuum 400 Series (PA-7100) Technical Service Guide (no URL)
- The Stratus Continuum Family (URL gone)
- Stratus Continuum 400 Series Fault-Tolerant HP-UX Servers, Stratus Technologies 2003
- Stratus Continuum Products 600 and 1200, Stratus Technologies 2003
- Stratus Machine History (August 2017: Paul Green. Accessed March 2021)
- Stratus HP-UX Brochure, Stratus 2004 archive.org
- Stratus VOS Operating System, Count on Stratus, Stratus 2004 archive.org Stratus Continuum Series - VOS, Stratus Virtual Operating system, Stratus 2003 archive.org SVOS Software Release Bulletins, Stratus 2004, FTP archive.org
- Continuum 600/1200 Series (PA-7100) Service Announcement, Stratus 1998 archive.org
- Stratus Shifts High-End Servers From PA-RISC to Intel, Computer World 2004
- Stratus Continuum 600/1200 Series Systems, cabinet llustration and parts, Stratus customers service
- Servers in the Stratussphere, HP Professional June 1999 archive.org