Document revision date: 30 March 2001

This chapter describes the use of disk drivers that support the disk devices listed in the Software Product Description for the OpenVMS Operating System for Alpha and VAX. The chapter also includes descriptions of many of the supported disks and controllers. However, not all supported devices are described here. Refer to the Software Product Description for the OpenVMS Operating System for Alpha and VAX for the definitive list of supported devices.

All disk drivers support Files-11 On-Disk Structure Level 1 and Level 2 file structures. Access to these file structures is through the DCL commands INITIALIZE and MOUNT, followed by the RMS calls described in the OpenVMS Record Management Services Reference Manual. Files in RT-11 format can be read or written with the file exchange facility EXCHANGE.

2.1 Supported Disk Devices and Controllers

The following sections provide descriptions of disk devices.

To obtain more information about a device, use the DCL command SHOW DEVICE with the /FULL qualifier, the Get Device/Volume Information ($GETDVI) system service (from a program), or the F$GETDVI lexical function (in a command line or command procedure). Section 2.3 lists the information on disk devices returned by $GETDVI.

2.1.1 UDA50 UNIBUS Disk Adapter

The UDA50 UNIBUS Disk Adapter is a microprocessor-based disk controller for mass storage devices that implements the DIGITAL Storage Architecture (DSA); for more information on the DSA, see Section 2.2.3.

The UDA50 controller is used to connect any combination of four RA60, RA80, and RA81 disk drives to the UNIBUS. Two UDA50 controllers can be attached to a single UNIBUS for a maximum of eight disk drives per UNIBUS. On the VAX-11/780 processor, the operating system supports one UDA50 on the first UNIBUS, which can accommodate certain other options. Adding a second UDA50 requires a second UNIBUS. With the exception of the first UNIBUS, a maximum of two UDA50 controllers per UNIBUS are supported. If two UDA50 controllers are on a UNIBUS, no other options can be placed on that UNIBUS. The VAX-11/730 processor supports only one UDA50 per UNIBUS.

The UDA50, in implementing DSA, takes over the control of the physical disk unit. The operating system processes request virtual or logical I/O on disks controlled by the UDA50. The operating system maps virtual block addresses into logical block addresses. The UDA50 then resolves logical block addresses into physical block addresses on the disk.

The UDA50 controller corrects bad blocks on the disk by requesting that the disk class driver revector a failing physical block to another, error-free physical block on the disk; the logical block number is not changed (see Section 2.2.11.1). Any bad blocks that might exist on a disk attached to a UDA50 are transparent to the operating system, which does logical or virtual I/O to such a disk. The UDA50 also corrects most data errors.

2.1.2 KDA50 Disk Controller

The KDA50 disk controller is a two-module disk controller that allows the RA-series DSA disk drives to be attached to Q-bus systems. The KDA50 performs the same functions as the UDA50 (see Section 2.1.1).

2.1.3 KDB50 Disk Controller

The KDB50 disk controller is a two-module disk controller that allows the RA-series DSA disk drives to be attached to BI bus systems, such as the VAX 8200 processor. The KDB50 performs the same functions as the UDA50 (see Section 2.1.1).

2.1.4 HSC40, HSC50, and HSC70 Controllers

HSC controllers are high-speed, high-availability controllers for mass storage devices that implement the DIGITAL Storage Architecture (DSA); for more information about the DSA, see Section 2.2.3. An HSC controller is connected to a processor by a CI bus (computer interconnect). The operating system supports the use of the HSC controllers in controlling the RA family of disks.

The HSC40 can support up to 12 SDI (standard disk interface) disks from the SA or RA families of disk drives or a combination of up to 12 SDI disk drives and TA-series tape drives.

The HSC70 can support up to 32 SDI disks from the SA or RA families of disk drives or a combination of SDI disk drives and TA-series tape drives.

HSC controllers, in implementing DSA, take over the control of the physical disk unit. System processes request virtual or logical I/O on disks controlled by the HSC controller. The operating system maps virtual block addresses into logical block addresses. The HSC controller then resolves logical block addresses into physical block addresses on the disk.

HSC controllers correct bad blocks on the disk by revectoring a failing physical block to another, error-free physical block on the disk; the logical block number is not changed. The operating system, which performs logical or virtual I/O to such a disk, does not recognize that any bad blocks might exist on a disk attached to an HSC controller. HSC controllers also correct most data errors.

The HSC series of controllers provides access to disks despite most hardware failures. Use of an HSC controller permits two or more processors to access files on the same disk.

HSC-series controllers allow you to add or subtract disks from the device configuration without rebooting the system.

2.1.5 SII Integral Adapter

The SII integral adapter on the MicroVAX 3300/3400 processor provides access through the DIGITAL Storage Systems Interconnect (DSSI) bus to a maximum of seven storage devices.

The term dual-host refers to pairs of CPUs connected to a bus. In dual-host configurations of MicroVAX 3300/3400 CPUs, the DSSI bus must be connected between the SII integral adapters present on both CPUs.

A maximum of six devices can be connected to the EDA640 adapter, which is implemeneted by the SII chip, DXX chip, and 128K RAM chip, in dual-host configurations.

2.1.6 KFQSA Adapter

The KFQSA adapter allows a maximum of seven storage devices for use on Q-bus systems.

In dual-host configurations of MicroVAX 3800/3900 CPUs, the DSSI bus must be connected between KFQSA adapters present on both CPUs.

A maximum of six devices can be connected to the KFQSA adapter in dual-host configurations.

2.1.7 RQDX3 Disk Controller

The RQDX3 controller is a Q-bus controller used with the RD series of Winchester-type disk drives and the RX33 and RX50 flexible diskette drives.

2.1.8 RA70 and RA90 Disk Drives

The RA70 is a 5.25-inch 280 MB high-performance DSA disk drive that uses thin-film media. It has an average access time of 27.0 ms and average seek time of 19.5 ms. The RA70 uses the Standard Disk Interface (SDI) and the KDA50 controller, and can be dual-ported.

The RA90 is a 1.2 GB disk drive designed with thin-film heads and 9-inch thin-film media with an average seek time of 18.5 ms. The RA90 conforms to DSA and uses the SDI. Both the RA70 and RA90 disk drives can be connected to medium-sized systems with the HSC-series controllers, KDB50, or UDA50 controllers.

2.1.9 RA60 Disk

The RA60 device uses high-capacity, removable media that provides 205 MB of usable storage (7.5 million bits of data per square inch) with transfer rates of 1.9 MB per second (burst) and 950 kb per second (sustained). The RA60 belongs to the DIGITAL Storage Architecture (DSA) family of disk devices (see Section 2.2.3). It is connected to either a UNIBUS Disk Adapter (UDA50) or an HSC50 controller. Up to four disk drives can be connected to each UDA50. Up to 24 disk drives can be connected to each HSC50.

2.1.10 RA80/RB80/RM80 and RA81 Fixed-Media Disks

The R80 disk drive is a high-capacity, moving-head disk whose nonremovable media consists of 14 data surfaces. Depending on how it is connected to the system, the R80 is identified internally as an RA80, RB80, or RM80, as follows:

• RA80---An R80 connected to the system through a UNIBUS disk adapter (UDA50) or an HSC50 controller. Up to four disk drives can be connected to each UDA50. Up to 24 disk drives can be connected to each HSC50.
• RB80---On VAX systems, an R80 connected to the system through an RB730 controller on a VAX-11/730 processor. Of the maximum of four drives that can be connected to an RB730 controller, only one can be an RB80.
• RM80---On VAX and Alpha systems, an R80 connected to the system through a MASSBUS adapter (MBA). Up to eight disk drives can be connected to each MBA.

The RA81 is a high-capacity disk drive with nonremovable media that can hold more than 890,000 blocks of data. This translates into more than 455 MB per spindle. The RA81 is connected to a UDA50 or an HSC50 controller. Up to four disk drives can be connected to each UDA50. Up to 24 drives can be connected to each HSC50.

The RA80 and RA81 belong to the DIGITAL Storage Architecture (DSA) family of disk devices (see Section 2.2.3).

2.1.11 RB02 and RL02 Cartridge Disk (VAX Only)

On VAX systems, the RL02 cartridge disk is a removable, random-access mass storage device with two data surfaces. The RL02 is connected to the system by an RL11 controller that interfaces with the UNIBUS adapter. Up to four RL02 disk drives can be connected to each RL11 controller. For physical I/O transfers, the track, sector, and cylinder parameters describe a physical 256-byte RL02 sector (see Section 2.4).

When the RL02 is connected to an RB730 controller on a VAX-11/730 processor, it is identified internally as an RB02 disk drive. Disk geometry is unchanged and RL02 disk packs can be exchanged between drives on different controllers. Up to four drives can be connected to the RB730 controller.

2.1.12 RC25 Disk (VAX Only)

On VAX systems, the RC25 disk is a self-contained, Winchester-type, mass storage device that consists of a disk adapter module, a disk drive, and an integrated disk controller. The drive contains two 8-inch, double-sided disks. One of the disks (RCF25) is a sealed, nonremovable, fixed-media disk. The other disk is a removable cartridge disk that is sealed until it is loaded into the disk drive. The disks share a common drive spindle, and together they provide 52 million bytes of storage. Adapter modules interface the RC25 with either a UNIBUS system or a Q-bus system.

2.1.13 RD53 and RD54 Disks (VAX Only)

On VAX systems, the RD53 and RD54 are 5.25-inch, full-height, Winchester-type drives with average access time of 38 ms and a data transfer rate of 0.625 MB per second. The RD53 and RD54 have a formatted capacity of 71 MB and 159 MB, respectively. When used with the RQDX3 controller, the RD53 and RD54 are DSA disks.

See Section 2.2.12 for information about using RD series disks on the VAXstation 2000.

2.1.14 RF30 and RF71 Disks

The RF30 is a 150-MB, 5.25-inch, half-height disk drive while the RF71 is a 400-MB full-height disk drive. The RF30 and RF71 include an embedded controller for multihost access and a mass storage control protocol (MSCP) server. The RF71 has a peak data transfer rate of 1.5 MB per second with average seek and access time of 21 ms and 29 ms, respectively.

Both the RF30 and RF71 disks use DIGITAL Storage System Interconnect (DSSI) bus and host adapters.

2.1.15 RK06 and RK07 Cartridge Disks (VAX Only)

On VAX systems, the RK06 cartridge disk is a removable, random-access, bulk storage device with three data surfaces. The RK07 cartridge disk is a double-density RK06. The RK06 and RK07 are connected to the system by an RK611 controller that interfaces to the UNIBUS adapter. Up to eight disk drives can be connected to each RK611.

2.1.16 RM03 and RM05 Pack Disks (VAX Only)

On VAX systems, the RM03 and RM05 pack disks are removable, moving-head disks that consist of five data surfaces for the RM03 and 19 data surfaces for the RM05. These disks are connected to the system by a MASSBUS adapter (MBA). Up to eight disk drives can be connected to each MBA.

2.1.17 RP05 and RP06 Disk (VAX Only)

On VAX systems, the RP05 and RP06 removable disks consist of 19 data surfaces and a moving read/write head. The RP06 removable disk has approximately twice the capacity of the RP05. These disks are connected to the system by an MBA. Up to eight disk drives can be connected to each MBA.

2.1.18 RP07 Fixed-Media Disk (VAX Only)

On VAX systems, the RP07 is a 516-MB, fixed-media disk drive that attaches to the MASSBUS of the VAX-11/780 system. The RP07 transfers data at 1.3 million bytes per second or as an option at a peak rate of 2.2 million bytes per second. The nine platters rotate at 3600 rev/min and their data is accessed at an average speed of 31.3 ms. These disks are connected to the system by an MBA. Up to eight disk drives can be connected to each MBA.

2.1.19 RRD40 and RRD50 Read-Only Memory (CD-ROM)

The RRD40 and RRD50 are compact disc read-only memory (CD-ROM) devices that use replicated media with a formatted capacity of approximately 600 MB.

The RRD40 is a 5.25-inch half-height, front-loading tabletop or embedded device that attaches to the system using either the Small Computer System Interface (SCSI) or Q-bus interface.

The RRD50 is a 5.25-inch, top-loading tabletop device that attaches to the system using a Q-bus interface.

The RRD40 has an average access time of 0.5 second while the average access time for the RRD50 is 1.5 seconds. Both the RRD40 and RRD50 have a data transfer rate of 150 KB per second.

The media for the RRD40 and the RRD50 are removable 4.7-inch (120-mm) compact discs. However, the media for the RRD40 are enclosed in protective self-loading carriers. The RRD40 with a SCSI interface is also available as an embedded unit. The RRD40 and RRD50 Q-bus subsystems are standard disk MSCP devices.

2.1.20 RX01 Console Disk (VAX Only)

On VAX systems, the RX01 disk uses a diskette. The disk is connected to the LSI console on the VAX-11/780, which the driver accesses using the MTPR and MFPR privileged instructions.

For logical and virtual block I/O operations, data is accessed with one block resolution (four sectors). The sector numbers are interleaved to expedite data transfers. Section 2.2.10 describes sector interleaving in greater detail.

For physical block I/O operations, the track, sector, and cylinder parameters describe a physical, 128-byte RX01 sector (see Figure 2-1 and Section 2.4). Note that the driver does not apply track-to-track skew, cylinder offset, or sector interleaving to this physical medium address.

Figure 2-1 Disk Physical Address

On VAX systems, the RX02 disk is a mass storage device that uses removable diskettes. The RX02 supports existing single-density, RX01-compatible diskettes. A double-density mode allows diskettes to be recorded at twice the linear density. An entire diskette must be formatted in either single or double density. Mixed mode diskettes are not allowed.

The RX02 is connected to the system by an RX211 controller that interfaces with the UNIBUS adapter. Up to two disk drives can be controlled by each RX211.

For logical and virtual block I/O operations, data is accessed with single block resolution (four single-density sectors or two double-density sectors). The sector numbers are interleaved to expedite data transfers. Section 2.2.10 describes this feature in greater detail.

For physical block I/O operations, the track and sector parameters shown in Figure 2-1 describe a physical sector (128 bytes in single density; 256 bytes in double density). The driver does not apply track-to-track skew, cylinder offset, or sector interleaving to the physical medium address.

2.1.22 RX23 (VAX Only)

On VAX systems, the RX23 device is a 1-inch high, flexible diskette drive that uses 3.5-inch microfloppy diskettes. The RX23 drive can access standard- and high-density media. The following table summarizes capacities for standard- and high-density media:

Density	Unformatted	Formatted
Standard	1.0 MB	700 KB
High	2.0 MB	1.4 MB

The RX23 is backward compatible in that it can read 1-MB media. It can also read and write 2.0-MB double-sided, high-density (135 tracks per inch) media.

The RX23 communicates with the controller using the ST506 fixed-disk interconnect (FDI).

2.1.23 RX33 (VAX Only)

On VAX systems, the RX33 is a 1.2-MB, 5.25-inch, half-height diskette drive. The RX33 can record in either standard- or high-density mode. High-density mode provides 1.2 MB of storage using 96 tracks per inch using double-sided, high-density diskettes.

In standard-density mode, the RX33 drive is read- and write-compatible with single-sided, standard-density RX50 diskettes.

2.1.24 RX50 (VAX Only)

On VAX systems, the RX50 dual-diskette drive stores data in fixed-length blocks on 5.25-inch 0.8-MB, flexible diskettes using preformatted headers. The RX50 can accommodate two diskettes simultaneously.

2.1.25 RZ22, RZ23, and RZ55 Disks

The RZ22 and RZ23 are 3.5-inch, half-height SCSI drives with an average seek rate of 33 ms and an average data transfer rate of 1.25 MB per second. The RZ22 and RZ23 have capacities of 52 MB and 104 MB, respectively.

The RZ55 is a 332-MB, 5.25-inch, full-height SCSI drive with an average access rate of 24 ms.

2.1.26 TU58 Magnetic Tape (DECtape II)

The TU58 is a random-access, mass storage magnetic tape device capable of reading and writing 256K bytes per drive of data on block-addressable, preformatted cartridges at 800 bits per inch. Unlike conventional magnetic tape systems, which store information at variable positions on the tape, the TU58 stores information at fixed positions on the tape, as do magnetic disk or floppy disk devices. Therefore, blocks of data can be placed on tape in a random fashion, without disturbing previously recorded data. In its physical geometry, the tape is conceptually viewed as having one cylinder, four tracks per cylinder, and 128 sectors per track. Each sector contains one 512-byte block.

The TU58 uses two vectors. NUMVEC=2 is required on the CONNECT command when specifying system parameters.

The TU58 interfaces with the UNIBUS adapter through a DL11-series interface device. Both the TU58 and the DL11 should be set to 9600 baud. (Because the TU58 is attached to a DL11, the user cannot directly access the TU58 registers if the TU58 is on the UNIBUS.) The TU58, which has its own controller, can access either one or two tape drives.

2.2 Driver Features

Disk drivers provide the following features:

• Multiple controllers of the same type (except RB730), for example, more than one MBA or RK611 can be used on the system
• Multiple disk drives per controller (the exact number depends on the controller)
• Different types of disk drives on a single controller
• Static dual porting (MBA drives only)
• Overlapped seeks (except RL02, RX01, RX02, and TU58)
• Data checks on a per-request, per-file, or per-volume basis (except RX01 and RX02)
• Full recovery from power failure for online disk drives with volumes mounted
• Extensive error recovery algorithms, such as error code correction and offset (except RB02, RL02, RX01, RX02, and TU58); for DSA disks, these algorithms are implemented in the controller
• Dynamic, as well as static, bad block handling
• Logging of device errors in a file that can be displayed by field service personnel or customer personnel
• Online diagnostic support for drive level diagnostics
• Multiple-block, noncontiguous, virtual I/O operations at the driver level
• Logical-to-physical sector translation (RX01 and RX02 only)

The following sections describe these features in greater detail.

2.2.1 Dual-Pathed Disks

A dual-pathed disk is a dual-ported disk that is accessible to all the CPUs in the cluster, not just to the CPUs that are connected physically to the disk. Dual-pathed disks can be any of the following:

• Dual-ported MASSBUS disks
• Dual-ported HSC disks
• Dual-pathed DSA disks on local UDA50, KDA50, and KDB50 controllers
• Dual-ported RF-series disks

The term dual-pathed refers to the two paths through which clustered CPUs can access a disk to which they are not directly connected. If one path fails, the disk is accessed over the other path. (Note that with a dual-ported MASSBUS disk, a CPU directly connected to the disk always accesses it locally.)

2.2.2 Dual Porting MASSBUS Disks

The MASSBUS disk drivers, DBDRIVER and DRDRIVER, support static dual porting. Dual porting allows two MASSBUS controllers to access the same disk drive. Figure 2-2 shows this configuration. The RP05, RP06, RP07, RM03, RM05, and RM80 disk drives can be ordered, or upgraded in the field, with the MASSBUS dual-port option.

Figure 2-2 Dual-Ported Disk Drives

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