The document provides an overview of distributed file systems including NFS, Lustre, AFS, Coda, and Sprite. It discusses key concepts such as naming, caching, consistency, performance, replication, and security. Examples of different distributed file system architectures and consistency models are presented. Key goals and tradeoffs for different distributed file systems are outlined.
1. 03-10-09 Some slides are taken from Professor Grimshaw, Ranveer Chandra, Krasimira Kapitnova, etc
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63. User process –> open file F The kernel resolves that it’s a Vice file -> passes it to Venus D is in the cache & has callback – > use it without any network communication D is in cache but has no callback – > contact the appropriate server for a new copy; establish callback D is not in cache – > fetch it from the server ; establish callback File F is identified -> create a current cache copy Venus returns to the kernel which opens F and returns its handle to the process
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Notas do Editor
File is a named collection of related information that is recorded on some permanent storage
Access transparency – Use same mechanism to access file whether it is local or remote, i.e., map remote files into local file system name space
Harder to mark failure Performance issues – caching etc? Can’t really do
COTS Legacy apps Does it really matter where it is? One copy versus many copies Etc
Lampson –hints for push model
A server exports one or more of its directories to remote clients Clients access exported directories by mounting them The contents are then accessed as if they were local
Pros: server is stateless, i.e. no state about open files Cons: Locking is difficult, no concurrency control
No consistency semantics – things marked dirty flushed within 30 seconds Checks non-dirty items every 5 seconds Bad performance with heavy load etc
User process wants to open a file with a pathname P The kernel resolves that it’s a Vice file & passes it to Venus on that workstation One of the LWP’s uses the cache to examine each directory component D of P… When processing a pathname component, Venus identifies the server to be contacted by examining the volume field of the Fid. Authentication, protection checking, and network failures complicate the matter considerably.
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