1998-01-09 09:35:18 +03:00
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.\" $NetBSD: rvd.4p,v 1.3 1998/01/09 06:35:24 perry Exp $
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1994-06-19 04:07:16 +04:00
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.\"
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.\" 5799-WZQ (C) COPYRIGHT IBM CORPORATION 1986,1987,1988
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.\" LICENSED MATERIALS - PROPERTY OF IBM
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.\" REFER TO COPYRIGHT INSTRUCTIONS FORM NUMBER G120-2083
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.\"
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1994-06-19 05:13:13 +04:00
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.\"WISC: Header:rvd.4p_ca 11.0$
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.\"WISC: ACIS:rvd.4p_ca 11.0$
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.\"WISC: Source: /ibm/acis/usr/man/man4/RCS/rvd.4p_ca,v $
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1994-06-19 04:07:16 +04:00
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.\"This file contains -man macros.
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.TH RVD 4P "July 1987" "Space overwritten by .AC macro" " "
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.AC 1 0
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.SH NAME
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rvd \- Remote Virtual Disk protocol
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.SH DESCRIPTION
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RVD
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is a network service which allows several
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physical machines to share one
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physical mass storage device such as a hard disk. The basic
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concept is to have the machine to which the device is physically attached
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act as a server to read and write blocks for all the other
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machines desiring use of the resource.
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.PP
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The server program apportions the
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physical blocks into \*(lqvirtual disk packs\*(rq based on a
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table maintained with
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.IR vddb (8).
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The packs can then be used separately by clients. There are
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three modes of use: read-only, shared, and exclusive.
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Exclusive mode is used for
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read-write access, while read-only mode is as it sounds.
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Shared mode is not supported under IBM/4.3.
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If a disk pack is \*(lqspun up\*(rq in read-only mode,
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several clients may share the pack and read its information. In
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exclusive mode, one client has exclusive use of the disk pack.
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.PP
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Packs are \*(lqspun up\*(rq and \*(lqspun down\*(rq with the
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.I up
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and
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.I down
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commands (see
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.IR up (1)).
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This can be done
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at reboot time within
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.I /etc/rc.local
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(see
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.IR rc (8))
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or
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at login time within
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.I ~/.login
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(see
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.IR csh (1)).
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Once a pack is spun up, it behaves like a disk physically attached to
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the local machine (excepting network latency).
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The client can do anything desired with the pack;
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both MS-DOS and UNIX operating system file systems have
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been used on the same physical
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drive at the same time (on separate packs, of course).
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.PP
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RVD
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is implemented in two parts: server code and client code. The server
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code is written as a
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.IR "user process" ,
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i.e. it does not require any special
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privileges beyond read/write access to the disks it manages. The server
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opens a network socket and listens for UDP connections. It also accepts
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all
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RVD
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packets and acts on them.
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RVD is a protocol different from both
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UDP and TCP,
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although similar in nature to the former.
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.PP
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The client code is implemented as a pseudo-device and corresponding
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device driver in the kernel. It can handle up to 10
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remote virtual disks
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simultaneously, which are associated with the pseudo-devices below.
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.SH FILES
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.DT
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/dev/vd[0-9]a block special file pseudo-device
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.br
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/dev/rvd[0-9]a character special file pseudo-device
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.SH "SEE ALSO"
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up(1), rvddb(5), rvdtab(5),
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rvdflush(8), rvdchlog(8), rvddown(8),
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rvdexch(8), rvdflush(8), rvdlog(8), rvdsend(8), rvdshow(8),
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rvdshut(8), rvdsrv(8), savervd(8),
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spinup(8), vddb(8), vdstats(8)
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.br
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``The Remote Virtual Disk System'' in Volume II, Supplementary Documents
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