SLIDE 1
Traditional Memory Interfaces
Process Virtual Memory File Management Physical Memory Storage Devices Device Interface Secondary Memory Interface Primary Memory Interface
Remote Files Traditional Memory Interfaces Process Primary Memory - - PowerPoint PPT Presentation
Remote Files Traditional Memory Interfaces Process Primary Memory - - PowerPoint PPT Presentation
Remote Files Traditional Memory Interfaces Process Primary Memory Interface Secondary Memory Interface Virtual File Memory Management Device Interface Physical Storage Memory Devices Explicit File Copying Need a way for a process
SLIDE 2
SLIDE 3
Explicit File Copying
¥ Need a way for a process on one machine to pass info to a process on another machine ¥ Technique
Ð Sender writes a file Ð User manually copies file to a remote machine Ð Receiver opens the file and reads it
¥ Very coarse grained ¥ Very high latency
SLIDE 4
Multics Segmented Memory
Process Segmented Virtual Memory File Management Physical Memory Storage Devices Device Interface Secondary Memory Interface Primary Memory Interface Normal data flow Alternative data flow
SLIDE 5
Remote Secondary Memory
Process File Management Storage Devices Device Interface Secondary Memory Interface Comm Network Client Interface to Remote Store
SLIDE 6
Refined View
Process File Management Storage Devices Secondary Memory Interface Comm Network Remote Access Storage Devices Remote Secondary Storage Client Machine Server Machine
SLIDE 7
Refined View
Process File Management Storage Devices Secondary Memory Interface Comm Network Remote Access Storage Devices Remote Secondary Storage Client Machine Server Machine
¥Server is a remote disk ¥Client & server implement file manager ¥Replicate file mgrs, then copy files
SLIDE 8
Remote Disk Server
General File Management Storage Devices Comm Network Virtual Disk Driver Storage Devices Remote Disk Application Client Machine Server Machine
file mgr: diskRequest(details); VDD: Pack parameters; VDD: Send request; (wait for response)
SLIDE 9
Remote Disk Server
General File Management Storage Devices Comm Network Virtual Disk Driver Storage Devices Remote Disk Application Client Machine Server Machine
file mgr: diskRequest(details); VDD: Pack parameters; VDD: Send request; (wait for response) (waiting for a request) RDA: Unpack parameters; RDA: Generate local disk request; (waiting) RDA: Generate reply; RDA: Send reply (waiting for a request)
SLIDE 10
Remote Disk Server
General File Management Storage Devices Comm Network Virtual Disk Driver Storage Devices Remote Disk Application Client Machine Server Machine
file mgr: diskRequest(details); VDD: Pack parameters; VDD: Send request; (wait for response) (waiting for a request) RDA: Unpack parameters; RDA: Generate local disk request; (waiting) RDA: Generate reply; RDA: Send reply (waiting for a request) VDD: Receive reply; VDD: Unpack parameters; VDD: Return to file mgr
SLIDE 11
Performance & Reliability
¥ Became commercially feasible in about 1986 ¥ Biggest concern was reliability
Ð Reliable command execution
¥ Time-outs ¥ Idempotent disk operations
Ð Crash recovery
¥ Stateless servers
¥ Forerunner of the Ònetwork computerÓ
SLIDE 12
Remote File Server
General File Management Storage Devices Comm Network Client Part of Remote File System Storage Devices Server Part of Remote File System Client Machine Server Machine
¥Read/write management ¥Pack/unpack byte stream ¥Buffering ¥... ¥Block management ¥Buffering ¥Device management ¥...
SLIDE 13
Block Caching
¥ Widely used in all file systems ¥ In RFS can buffer at:
Ð Server
¥ DoesnÕt avoid network latency
Ð Client
¥ Consistency ¥ Sometimes use sequential write consistency (no sharing if there are multiple writers)
SLIDE 14
Crash Recovery
¥ Client has a file open and server crashes
Ð Distributed state makes recovery difficult Ð Can counteract with a stateless server Ð But it requires that state be transmitted with every service request
¥ Recovery-oriented file service, e.g., Sun NFS ¥ Performance-oriented file service
SLIDE 15