The Distributed V Kernel and its Performance for Diskless Workstations

Take-away points

• message-oriented
• diskless workstations
• streamingly send file

Overview

• V Kernel is a message-oriented kernel
• used in an eviroment of diskless workstations connected by a high-speed local network to a set of file servers.

• Advantage

  1. lower hardware cost per workstation
  2. simpler maintenace and economies of scale with shared file servers.
  3. little or no memory or processing overhead on the workstation for file system and disk handling.
  4. fewer problem with relication, consistency and distribution of files.

• Disadvantate

  • overhead of preforming all file access over the network
    • use streaming protocals to minimize the effect of network lantecy on performance (sequential file access is common)

Interprocess Communication

• pid: process identifier
• all message are a fixed 32 bytes in length
• No buffering & queueing problem, move directly from source address space into the NIC, and directly from the NIC to the destination address space
• MoveTo and MoveFrom for transferring a large amount of data (between remote processes)

Implementation

Process Naming

• global (flat) naming space
• pid: logical host identifier (16-bit) + locally unique identifier (16-bit).
• a table maps logical hosts to network addresses.

Remote Data Transfer

• MoveTo and MoveFrom: transfer a large amount of data bwtween remote processes with a minimal time increase.

Page-level File Access

• page read -- Send-Receive-ReplyWithSegment
• page write -- Send-ReceiveWithSegment-Reply