SCO OpenServer Release 6 Technical White Paper - Part 3

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SCO OpenServer Release 6 - A Look Inside

The SCO OpenServer Release 6 operating system is the most advanced deployment platform for industry standard Intel processor systems. It is the trusted foundation for solutions where proven scalability, reliability and affordability are critical. Whether powering large business critical applications or running a small- to medium-sized-business, SCO OpenServer Release 6 delivers the same scalability and reliability that is synonymous with UNIX Systems. SCO OpenServer Release 6 is offered in two distinct versions and a set of optional products.

Designed from the ground up to support business-critical solutions, SCO OpenServer Release 6 delivers operating system configurations designed to power departmental databases, application servers, intranet servers, and mail and messaging servers.

What's New in SCO OpenServer Release 6?

Below is a list of some of the key features that are new in SCO OpenServer Release 6.



Large scale memory

Support for up to 16GB of general purpose memory and 64GB of special-purpose (dedicated) memory.

Kernel-level threads

Unlike user-level threads, kernel-level threads can make use of multiple processors.

Improved Boot

  • Updated network boot and network install, utilizing PXE technology for media-less installs (available post FCS)
  • Install/boot above the 1024 cylinder/8GB boundary
  • Bootable CD-ROM support changed from floppy-emulation to non-emulation mode

Network Storage Device support

Fibre Channel, SAN, and NAS. HP StorageWorks Modular Smart Array (MSA) provides direct attach, small clusters, as well as entry-level and mid-range SAN environments.

Improved internal storage support

Including AHCI Serial ATA (SATA) and support for more than two Parallel ATA (PATA) controllers in a system. Serial Attached SCSI (SAS) is supported on HP Proliant systems.

Network Card support

New Gigabit support, better throughput with new stack, support for wireless

Optical media writing support

Full support for writing data CDs and DVDs, including internal and external drives (based on Cdrtools-ProDVD 2.01.01)

Expanded USB device support

  • USB 2.0 support for EHCI Host Controllers
  • USB 1.1 support for OHCI and UHCI Host Controllers
  • Bootable USB CD-ROM support
  • USB printer support
  • Class Drivers, including Keyboards, Pointing Devices, CD-ROMs, Floppy, and Mass Storage Devices

ACPI support

Includes detection of hyper-threaded CPUs

New Intel and AMD Processor support

Intel Pentium® 4, AMD® Athlon, Athlon XP, Duron, Athlon 64, and Opteron®

Integrated encryption

The base 56-bit encryption utilities previously available as an add-on package have been integrated into SCO OpenServer Release 6. Support for filesystem encryption has also been added.

FAT32 and VFAT

Support for FAT32 and VFAT filesystem types has been added to allow mounting, reading and writing of these DOS filesystems.

Updated network protocols and services

New versions of the Apache web server, the Squid proxy server, TCP/IP performance improvements, and the Mozilla 1.7.8 browser.

Java 1.4

Support for Java 2, Standard Edition (J2SE), version 1.4.2

Database support

PostgreSQL and MySQL open source databases are included.

Windows application support

Windows XP and Windows 2000 applications can be run on SCO OpenServer Release 6 with MergePro (available post-FCS).


SCO OpenServer Release 6 Product Editions and Optional Services

SCO OpenServer Release 6 consists of two pre-configured editions and optional products to build and deploy UNIX applications. Whether you are powering a suite of business-critical applications or a small-to- medium-sized business, there is an edition of SCO OpenServer Release 6 to satisfy your requirements. These editions are complemented by a range of optional services and development tools. SCO OpenServer Release 6 Editions include:

Enterprise Edition

An advanced operating environment suitable for departmental database and application servers typically found in medium- to large-sized business environments. For departmental servers in medium or large organizations to run applications and reliably share business critical information with a wide range of client devices. The Enterprise Edition is licensed for four CPUs, ten users and four gigabytes of memory.

Starter Edition

Suitable for small business customers, or as a file and print server, or edge of network server in large accounts. The default configuration is two users, one gigabyte of memory and one CPU. Special additional user (five-user bump packs; normal bumps do not work), memory and CPU licenses. Also upgradeable to Enterprise.


Bundled product and support as option

Bundled and optional product support is available with all new system, upgrade, and trade-in licenses. Support bundled with product includes:

Traditional "Break-fix" support

  • Six month contract
  • Two Authorized callers
  • Phone/fax/email delivery
  • Unlimited Service Requests
  • Six business hour response time
  • Ability to uplift
  • Add-on options available

Bundled support is offered per OS installation/server, with registration required to enable the service.

Enterprise Scalability and Performance

Key to the success of such a computing paradigm is the Reliability, Availability, and Scalability (RAS) of the server platform. SCO OpenServer Release 6 extends the class of systems supported with the incorporation of a number of scalability and availability enhancements that meet the requirements of the most demanding applications and workloads.

Optimized, High Performance Kernel

SCO OpenServer Release 6 is built from the System V Release 5 (SVR5) UNIX kernel. Leveraging more than 25 years of knowledge and experience gained in operating systems development, SVR5 builds upon the inherent strengths of SVR3 and SVR4 ® environments (with which it is fully compliant) for highly reliable enterprise computing. This advanced kernel is fully multi-threaded with fine-grained locking, delivering increased scalability and better real-time performance. Light-weight processes (LWPs) allow parallel execution of multiple threads for the same process, delivering faster response to transaction-based routines such as web servers. The process scheduler allows timesharingandfixed-priority workloads, enabling the system to be used for a variety of applications simultaneously. For example, near real-time process scheduling is particularly important in manufacturing process control, while time-sharing is more typical for business applications (such as databases). Mature SMP technology is built into the kernel that SCO has evolved and perfected over the last decade, yielding an operating system that provides unparalleled levels of scalability. SCO operating systems have been shown to scale well in environments up to 16 processors (with 32 being the maximum). This results in outstanding performance on competitive benchmarks, beating not only other Intel-based operating systems, but RISC-based platforms as well.

Memory allocation for various kernel resources is fully dynamic: the system automatically tunes itself to respond to variations in workloads, and allows flexibility in performance tuning. Kernel modules can be loaded and unloaded dynamically, optimizing the use of available memory and other system resources.

Each of the kernel data structures that keep track of users, groups, processes and devices now use expanded type sizes, yielding a greater number of system-wide UIDs, GIDs, PIDs, devices and inodes. This results in a system that is much more scalable in terms of the users it can support and resources it can provide. The maximum default process size supported is 3.0GB, but by restricting kernel virtual space it can be increased to approximately 3.75GB.

Large Scale Memory

SCO OpenServer Release 6 supports Large Physical Memory (LPM) and can utilize up to 64GB of physical memory. System memory (RAM) configurations up to 16GB in size are supported for general-purpose workloads. Memory above 16GB can be used as dedicated memory that is set aside at system initialization time for use by specific shared memory facilities. SCO OpenServer Release 6 uses the Physical Address Extension (PAE) mode of the Pentium 4 processor when operating with more than 4GB of memory.

Data Storage Features

SCO OpenServer Release 6 supports a number of features that enable reliable, scalable storage solutions.

Multipath I/O (MPIO)

MPIO allows multiple Host Bus Adapters (HBAs) to be connected to the same bus and multiported devices. MPIO delivers significant performance benefits using load balancing. Fulfilling I/O requests in a round-robin fashion on each available active I/O path to a disk, it maximizes disk loading while reducing traffic on individual SCSI buses. This also allows multiple systems in a cluster to read and write to all connected disks, thus minimizing bottlenecks for any single system or controller. Systems can be configured for alternate routes to disk storage, protecting against single points of failure in the I/O system. This ensures high availability to the devices when an HBA fails. Upon controller failure, the operating system will redirect I/O through another path to the device.

Large Scale Data Storage

The I/O subsystem in SCO OpenServer Release 6 is designed to meet the scalability needs of large SMP machines. It employs the UnixWare Storage Device Interface (SDI), a framework for driver software, for many of the hardware devices on a system. Besides organizing, simplifying, and standardizing the way device drivers are written, SDI also makes it easier to administer a wide variety of devices and interfaces. The system also supports a far greater number of independent disk storage devices than previous releases of OpenServer and other operating systems for Intel architecture servers. By extending the device addressing model, the system provides a potential 2^32 unique addresses for controllers, buses, and logical units. SCO OpenServer Release 6 supports the following types of physical mass storage devices:

Hard disks: high-speed, high-capacity disks available in a variety of types (IDE, SATA, SAS, SCSI, USB) and sizes. SCO OpenServer Release 6 supports both fixed and removable drives as well as industry standard hardware-RAID systems.

CD and DVD devices: SCO OpenServer Release 6 supports most disc readers and burners, including those using the IDE, SCSI, USB, or SATA interface.

Medium Changer devices: sometimes called jukeboxes, they are robotic mechanisms that automate the movement of storage media (whether tape or optical) between storage locations and physical read/write drives. Changer devices are ideal for creating large, centralized, highly scalable storage capacity.

 The hardware compatibility list is constantly being updated. For more information please visit:

Large Files and Filesystems

  • SCO OpenServer Release 6 supports a wide range of disk-based filesystem types, one of which supports 64-bitfile sizes (via the long long data type):
  • VxFS™ (the Veritas filesystem type; provides support for large files, large filesystems and journaling) – used as default
  • AFS (Advanced filesystem)
  • EAFS (Extended advanced filesystem)
  • HTFS (High throughput filesystem)
  • S51K (System V 1K filesystem)
  • cdfs (CD-ROM filesystem: ISO 9660/High Sierra, RockRidge, and Joliet extensions)
  • dosfs (DOS filesystem including FAT 32)
  • NFS (Network filesystem)

In addition, the system supports a number of non-disk based (pseudo) filesystems, some of which are mountable and some of which are not mountable. Some of the supported pseudo-filesystems include:

  • procfs (/proc filesystem) provides access to the state of each active process and LWP (Light Weight Process) in the system
  • profs (Processor filesystem) provides access to the state of each processor in the system
  • memfs (Memory filesystem).

The system supports the specifications defined by the Large File Summit (LFS), a set of extensions to the Single UNIX Specification (SUS) that support 64-bit filesystems on 32-bit systems. The Veritas filesystem (VxFS) supports large files and large filesystems, with maximum file and filesystem sizes up to 1TB. Independent of large filesystem support, each filesystem can support up to four billion files.

Filesystem Encryption

Filesystem encryption has been added to the marry driver. Using the marry command, an empty regular file is associated with a block special device name and encryption is enabled on the file. After a filesystem is created on the block special device and mounted, all data written to the file is encrypted using the 128 bit Advanced Encryption Standard (also known as 128bit AES and the Rijndael block cipher); all data read from the file is decrypted.

Improved network performance

Network performance has been significantly increased with several enhancements:

  • Checksum offloading reduces CPU overhead
  • MAC header collapsing improves transmit performance
  • Driver interface changes to reduce the number of memory allocations for every packet being transferred
  • Improvements in transferring packets for across-the-board STREAMS performance enhancement
  • Improved timer scheduling
  • Global time mutex lock split into multiple locks provides increased scalability for multiple simultaneous connections
  • Faster locks and other atomic primitives improves scalability and performance
  • File descriptor allocation algorithm improvements for scalability
  • Network multi-pathing allows multiple network connections ( failover support)

Kernel Debugging Tool (kdb)

As an aid to device driver developers for SCO OpenServer Release 6, the Kernel Debugger, called kdb is available for use with both editions. This tool supports debugging device drivers, and can be used to display kernel stack traces and various kernel structures, and allows modification of memory, I/O, and register contents.

Business Critical Reliability

The core of SCO OpenServer Release 6 leverages over 10 years of field-proven reliability and quality system software deployed in mission critical and business critical environments. SCO publishes Mean Time Between Software Stops (MTBSS) figures for SCO OpenServer Release 6, currently at over 20,000 hours. MTBSS figures have been adopted by leading OEMs as a metric for product reliability. Availability is also measured in the industry by “the 9s” rating. SCO OpenServer Release 6 achieves 99.99% availability – a rate unmatched on commodity hardware.

Hot Swap and Failover

The I/O subsystem of SCO OpenServer Release 6 supports new hardware technologies designed to improve the high-availability and fault-tolerance of the system. DDI8, the device driver subsystem includes support for systems with hot-pluggable storage, allowing drivers to be written so that failed or failing parts can be replaced without having to reconfigure the kernel and without taking the system down. SCO OpenServer Release 6 supports network card failover and hot-swappable SCSI storage devices. The SCSI hot add or hot remove feature allows for addition or removal of SCSI storage devices (hard disks, tape drives, CD-ROM drives) from a running system. Some uses of the features include:

  • Replacing a failed storage device on a system that must maintain high availability
  • Moving less frequently used devices (such as tape drives) between systems
  • Moving disk drives between systems to allow fast transport of data
  • Network Card Failover allows networking traffic to be shifted to another configured network adapter card when hardware failures are detected on the original card. The Network Configuration Manager can be used to configure a failover device for the primary NIC.

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