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General description

CHARON-AXP supports PCI I/O bypass controller for accessing to disk images and host physical disks.

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Loading PCI I/O bypass controller

Syntax for loading PCI I/O bypass storage adapter:

load pci_io_bypass <name>

The <name> can be DI<x>, DR<x> or DU<x>

where x is selected according to VMS naming scheme, i.e. A stands for the first controller of given type, B - for the second, etc.

Example:

load pci_io_bypass DIA

The adapter instance name ("DIA" in the example above) is used then for parametrization, for example:

set DIA container[0]="/Mydisks/vms_distributive.vdisk"

The numbers in the square brackets represent a number of device on PCI I/O Bypass controller.

The maximum number of I/O Bypass controller devices is 64.

By default I/O Bypass controller uses PCI slot corresponded to the <x> parameter (see above). If instead some particular slot is needed, refer to this section for details of specific placement of PCI peripherals on CHARON Virtual Machine (VM) PCI bus (note that "irq_bus" and "irq" parameters are ignored for I/O Bypass controller). In this case the <x> will be changed automatically according to custom position of I/O Bypass controller on PCI bus.

(info) I/O Bypass controller is implemented for OpenVMS only.

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Configuration parameters

The I/O Bypass controller has the following configuration parameters:

container

Parameter

container[N]

N is 0..32766 (no more than 64 units)

Type

Text String

Value

Possible values of the parameter are strings in one of the following forms:

  • Physical disk
    • "/dev/sd<L>" where "L" is letter.
    • "/dev/disk/by-id/..." - addressing by the disk ID, for example "/dev/disk/by-id/ata-ST1000DM003-9YN162_S1D01QJ4"
    • "/dev/disk/by-label/..." - addressing by the disk label, for example "/dev/disk/by-label/MyStorage"

    • "/dev/disk/by-uuid/..." - addressing by the disk UUID, for example "/dev/disk/by-uuid/0e808a2f-cdd3-4944-a245-f729ffd73882"
      (warning) Be careful not to destroy all the information from the disk dedicated to CHARON-AXP by mistake.

      "/dev/sd<L>" addressing is not persistent, so it is strongly recommended to use "/dev/disk/by-id/wwn-*" syntax instead to refer the disk by its WWID - especially in the enviroments utilizing FC and SAN storages.

       These disks must not be formatted by the host OS.

      Example:

      set DIA container[0]="/dev/sdb"

      It is also possible to use not a whole disk, but previously created partitions on it. In this case the syntax is the following: "/dev/sd<L><N>" where N is the number of partition to be used. 

      Example:

      set DIA container[0]="/dev/sdc1"

      .

  • Multipath disk
    • "/dev/dm-<N>" 
    • "/dev/mapper/mpath<N>" 
    • "/dev/mapper/disk<N>" 
      (warning) Be careful not to destroy all the information from the disk dedicated to CHARON-AXP by mistake.  

      These disks must not be formatted by the host OS.

      Example:

      set DIA container[100]="/dev/dm-0"

      .

  • Loop (virtual block) devices

    • "/dev/loop<N>"
      Example:

      set DIA container[200]="/dev/loop0"



  • Direct mapping to some SCSI disks

    • "/dev/sg<N>"
      Example:

      set DIA container[300]="/dev/sg0"

      .

  • ISO file for reading distribution CD-ROM image
    • [<drive>":\"<path-name>"\"]<file-name>[".iso"]
       Mapping may also include the full path (recommended), for example: "/my_disks/vms_distributive.iso"

      Example:

      set DIA container[600]="/my_disks/vms_distributive.iso"

      .

  • File representing a physical disk of the HP Alpha system (disk image)
    • [<drive>":\"<path-name>"\"]<file-name>[".vdisk"]
      These files can be created from scratch with "mkdskcmd" utility. Data and OS disk backups are transferred from the original system via tapes or network and restored into these container files.   

      Mapping may also include the full path, for example: "/my_disks/my_boot_disk.vdisk"

      Example:

      set DIA container[401]="my_dka401.vdisk"

This parameter is initially not set, thus creating NO storage elements on the controller.

removable

Parameter

removable[N]

N is 0..32766 (no more than 64 units)

TypeBoolean
Value

When set to "true", the removable configuration parameter instructs CHARON-AXP to report the corresponding virtual SCSI device as removable.

By default the removable configuration parameter is set to "false".

Example:

set DIA removable[400]=true

geometry

Parameter

geometry[N]

N is 0..32766 (no more than 64 units)

Type

Text String

Value

This formatted string value specifies the explicit geometry of the disk storage element. This parameter is not applicable to tape storage elements.

The string format is ”*/*/*/<B>" or ”*,*,*<B>" where B is the total size of the disk (in blocks) reported to the guest OS. If omitted it is calculated automatically.

If this parameter is not set, CHARON VM will configure the geometry based on the most probable disk type.

Initially not set.

use_io_file_buffering

Parameter

use_io_file_buffering[N]

N is 0..32766 (no more than 64 units)

TypeBoolean
Value

When set to "true", instructs CHARON-AXP to enable host operating system I/O cache on reading/writing operations.

(info) Note that this caching has a significant effect only in case of mapping to disk and tape containers, not physcial drives. 

When enabled, host operating system I/O cache may significantly improve I/O performance of the virtual system. At the same time maintaining I/O cache requires additional host resources (CPU and memory) which may negatively affect overall performance of the virtual system.

Initially is set to "false".

Example:

set DIA use_io_file_buffering[603]=true


When a disk image connected to an I/O Bypass controller is dismounted by OpenVMS, it is disconnected from CHARON-AXP and can be manipulated. It can be replaced with a different disk image if it keeps the same name. This capability may be useful when designing back-up and restore procedures. When copying CHARON-AXP disk images while CHARON-AXP is running, please take care to minimize the risk of overloading a heavily loaded CHARON-AXP host system. For example, using a sequential series of simple ftp binary copies is less resource intensive and thus less disruptive than multiple, simultaneous copies.

Empty disk images are created with the "mkdskcmd" utility. Tape images ("*.vtape") will be created automatically if they don't exist (no utility needed).

CHARON-AXP is able to boot from disk images of any OpenVMS/Alpha version.

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