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Disk Storage Devices for OpenVMS

Posted on December 30th, 2006 by Hoff
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If you are just starting out with OpenVMS hardware or looking to become more familiar with the hardware you have, you'll be learning about disks, and particularly about IDE-based ATA and ATAPI devices, and SCSI devices. This obviously for storage of data and of the operating system itself, but also at the disks used for the initial system installation and for software upgrades.

Also included here is a taxonomy of CD and DVD devices seen to operate with OpenVMS.

As when working on any computer system hardware or other electrically-powered devices, you can potentially cause serious and permanent damage to the hardware or even to yourself.

But as you are still reading here, what follows are some details of the disks typically configured with OpenVMS.

An Introduction to Disks

An OpenVMS system can operate diskless, booted as a satellite within an OpenVMS Cluster configuration. A completely diskless system is rare, however, as it is more efficient to maintain a disk cache for local memory (and potentially for accessing local copies of images or data), rather than paging across the network. (Information on diskless satellites in OpenVMS Cluster configurations is beyond the scope of this disk discussion.) More commonly, however, an OpenVMS system is configured with a local (usually SCSI) disk for the operating system, with zero or more disks for applications or local requirements, and with a bootable tape (older installations, and OpenVMS VAX only) or bootable CD drive (newer OpenVMS VAX, all OpenVMS Alpha) or bootable DVD (OpenVMS I64).

The major storage interconnects used with OpenVMS are SCSI, IDE ATA, IDE ATAPI and USB. The most common of these are SCSI for disks, and IDE ATAPI for OpenVMS Alpha and OpenVMS I64 CD and DVD devices.

IDE Disks

Only one system — the AlphaServer DS10L and AlphaServer DS10 series — has official support for booting IDE ATA disks.

While IDE disks in general can be speedy, the particular implementation of IDE disk support on OpenVMS configurations is not. IDE as implemented on OpenVMS is slow, and often much slower than SCSI.

There are restrictions around bootstraps from IDE ATAPI CD-ROM and DVD-ROM controllers, and specifically the Intel SIO series controllers used in some DIGITAL Personal Workstation series Alpha systems. Details on these controllers and on identifying the Intel SIO are available in the OpenVMS FAQ. Some of the Personal Workstation series systems do bootstrap from IDE ATAPI CD-ROM and DVD-ROM devices, and later Alpha and Integrity systems will generally bootstrap from IDE ATAPI CD-ROM and DVD-ROM devices.

Information on IDE disk capacity limits and related details are in IDE Bus, ATA disks and ATAPI (CD and DVD) on Alpha and Integrity Systems.

SCSI Disks

SCSI disks are far and away the most common disks for booting modern OpenVMS systems from locally-attached — Direct Attached Storage (DAS) devices — on recent VAX, Alpha and Integrity series systems.

Also see available information on StorageWorks and SureStore shelves and components.

Discussions of Fibre Channel (FC) Storage Area Network (SAN) disk devices and iSCSI NAS devices are beyond the scope of this discussion.

SCSI CD-R/RW and CD-ROM Devices

SCSI CD-R/RW and CD-ROM devices are now comparatively rare, but are the expected mechanism for loading SCSI-based OpenVMS VAX systems.

You must choose a SCSI CD device that defaults to 512-byte transfers, rather than the more common 2048-byte block transfers.

DIGITAL, Compaq and HP SCSI-based CD-ROM and DVD-ROM devices sold for use with OpenVMS will have 512-byte capability, and various hobbyists have reported success with Plextor-series SCSI PlexWriter CD-R/RW devices. Some OpenVMS Hobbyists have reported success with SCSI to IDE bridges, bridge devices which allow you to connect an IDE ATAPI CD or DVD devices to a SCSI bus. With these devices, you must ensure 512-byte operations and block-size conversions through the bridge.

Third-party SCSI Disks

If you plan to use SCSI disks from vendors other than DIGITAL, Compaq or HP, you will want to be using OpenVMS V6.2 or later, or (better) V7.1-2 or later. This because of changes in the SCSI driver stack within these two releases, and particularly changes that allowed the driver stack to better adapt to the individual behaviours of SCSI devices. (Older OpenVMS releases tend to return device errors around these disks, particularly due to driver expectations around the ARRE (Auto-Read Reallocation) and AWRE (Auto-Write Reallocation) settings.) The particular OpenVMS version is far less of a concern around those SCSI disk devices that DIGITAL, Compaq or HP support with OpenVMS, obviously. Additional details around device capacity limits and SCSI ECOs — particularly required for larger disks — are included in the OpenVMS FAQ.

Discussions of multi-host SCSI, Serial Attached SCSI (SAS), Network Attached Storage (NAS) or Fibre Channel (FC) or Computer Interconnect (CI) series Storage Area Networks (SANs) (arguably, configurations with CI and HSC50 and later HSC-series storage controllers were some of the earliest SAN configurations available) are beyond the scope of this particular discussion.

USB disks

USB devices are supported for bootstraps and for general disk operations on OpenVMS I64 systems, and for access with specific OpenVMS Alpha AlphaServer GS1280, AlphaServer ES47 and related series, and related configurations. Various of the Integrity servers have successfully bootstrapped OpenVMS I64 via (comparatively larger) USB disks.

With OpenVMS V8.2 and later, USB is integrated and available, where the host supports UCB connections. With V8.3, management and configuration is far easier, and the configuration of DN-class UCB disk devices is largely automatic. On OpenVMS V8.2 and V8.2-1, USB device configuration was a manual process.

On specific OpenVMS releases prior to V8.2, prototypes USB drivers are available for OpenVMS Alpha via the OpenVMS Freeware.

ATAPI CD and DVD Devices

No VAX systems have IDE ATAPI available as part of the base configurations nor as optional or add-on configurations (any SCSI IDE ATAPI bridges aside), nor do older Alpha systems. More recent OpenVMS Alpha systems and most (all?) OpenVMS I64 systems do have support for IDE ATAPI devices. As a general rule, AlphaServer and AlphaStation systems with numeric models will lack IDE ATAPI, while AlphaServer and AlphaStation series systems with alphanumeric models often have IDE ATAPI. When in doubt, always check the System and Options Catalog in the archives, or the Product Bulletin for configuration details and options.

Identification of CD and DVD devices

Various of the 512-byte block SCSI CD-ROM and CD-R/RW devices that have been seen to operate with various OpenVMS SCSI configurations, and that have been or are available on the used-equipment market, are listed below:

  • RRD40¹, 1x, LMSI, based on LMS CM210, requires the “antlers caddy”, no audio
  • RRD42¹, 1x, SCSI, based on Sony CDU-541, sliding-trap-door caddy
  • RRD43, 2x, SCSI, based on Toshiba XM-4101B
  • RRD44, 2x “high performance”, SCSI, Toshiba XM-3401B.
  • RRD45, 4x, SCSI, Toshiba XM-5401B.
  • RRD46, 12x, SCSI, Toshiba XM-5701B.
  • RRD47, 32x, SCSI, Toshiba XM-6201B.
  • RRD50¹, 1x, LMSI, LMS CM100 top-loader, no audio. Generally only seen on the oldest of MicroVAX systems, and with the RQD50 series Q-bus controller.
  • Plextor PlexWriter PX-W1210TS 12x 10x 32x, SCSI, CD-R/RW recorder
  • Plextor PlexWriter PX-W4012TS 40x 12x 40x, SCSI, CD-R/RW recorder
  • Plextor PX-716A IDE (not SCSI) DVD+R/RW CD-R/RW drive
  • HP A6986 (A6986-62001, A6986-64001, A6986-69001), slimline CD-RW/DVD-ROM, rx2600, based on Teac DW-224E

¹ indicates a drive that is viewed as less desirable by HoffmanLabs, variously due to its interface and/or its age and/or its implementation and/or its use of a caddy. Better choices are commonly available.

CD devices with 2048-byte defaults do not operate with OpenVMS SCSI drivers. (There are reports that OpenVMS V8.2-1 or V8.3 and later can allow read access to 2048-byte optical devices.)

Consult the HP platform support matrix for lists of supported devices for the various platforms. The Plextor series drives are not supported by HP.

Where the device permits recording, various of these have been used for CD or DVD recording on directly OpenVMS.

Enclosures, Mounting, Power and Cooling

Often overlooked, mounting and power can be critical to the longevity and reliability of a disk device. Disks that are operating with insufficient cooling can and will see shorter lifetimes or transient problems. In particular, installation of disks into older VAX or older Alpha system enclosures can overheat; these older enclosures may or may not provide sufficient cooling.

If the Systems and Options Catalog does not list the disk device as supported within the particular VAX or older Alpha enclosure and if you do not have the thermals of the disk (preferably 35°C or less) and of a disk that was supported within the enclosure, it is usually safest and easiest to mount the disk in an external enclosure, and particularly into an enclosure rated for the particular disk. The StorageWorks series or most any other similar SCSI shelf and associated disks is easy, flexible, and readily available. And if looking at the oldest StorageWorks shelves, do ensure that the BA35X-MD two-speed cooling fans are installed on the back of the BA356 shelf. These upgraded fans prominently feature their part numbers, and these are readily visible on the back of the BA356 shelf. Also ensure you have the blank covers installed in any open slots, as these maintain proper cooling.

Other related articles

Revisions

Newest first.

  • 18-Jun-2009: added a link
  • 13-Jun-2009: Reportedly OpenVMS SCSI drivers can de-block 2048 byte block devices starting with V8.2-1 or V8.3. This has not been confirmed.