红帽全球峰会第 2 章 Deploying an NFS server
By using the Network File System (NFS) protocol, remote users can mount shared directories over a network and use them as they were mounted locally. This enables you to consolidate resources onto centralized servers on the network.
2.1. Key features of minor NFSv4 versions
Each minor NFSv4 version brings enhancements aimed at improving performance and security. Use these improvements to utilize the full potential of NFSv4, ensuring efficient and reliable file sharing across networks.
Key features of NFSv4.2
- Server-side copy
- Server-side copy is a capability of the NFS server to copy files on the server without transferring the data back and forth over the network.
- Sparse files
- Enables files to have one or more empty spaces, or gaps, which are unallocated or uninitialized data blocks consisting only of zeros. This enables applications to map out the location of holes in the sparse file.
- Space reservation
- Clients can reserve or allocate space on the storage server before writing data. This prevents the server from running out of space.
- Labeled NFS
- Enforces data access rights and enables SELinux labels between a client and a server for individual files on an NFS file system.
- Layout enhancements
- Provides functionality to enable Parallel NFS (pNFS) servers to collect better performance statistics.
Key features of NFSv4.1
- Client-side support for pNFS
- The support of high-speed I/O to clustered servers enables you to store data on multiple machines, to provide direct access to data, and synchronization of updates to metadata.
- Sessions
Sessions maintain the state of the server relative to the connections belonging to a client. They provide two key features.
-
exactly-once-semantics(EOS) which helps to distinguish between the response of an old and new operation. - Bind multiple network connections for NFS operations, improving performance
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Key features of NFSv4.0
- RPC and security
-
The
RPCSEC_GSSframework enhances RPC security. The NFSv4 protocol introduces a new operation for in-band security negotiation. This enables clients to query server policies for accessing file system resources securely. - Procedure and operation structure
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NFS 4.0 introduces the
COMPOUNDprocedure, which enables clients to merge multiple operations into a single request to reduce RPCs. - File system model
NFS 4.0 retains the hierarchical file system model, treating files as byte streams and encoding names with UTF-8 for internationalization.
File handle types
With volatile file handles, servers can adjust to file system changes and enable clients to adapt as needed without requiring permanent file handles.
Attribute types
The file attribute structure includes required, recommended, and named attributes, each serving distinct purposes. Required attributes, derived from NFSv3, are essential for distinguishing file types, while recommended attributes, such as ACLs, provide enhanced access control.
Multi-server namespace
Namespaces span across multiple servers, simplify file system transfers based on attributes, support referrals, redundancy, and seamless server migration.
- OPEN and CLOSE operations
- These operations can combine file lookup, creation, and semantic sharing at a single point, ensuring correct file sharing semantics.
- File locking
- File locking is part of the protocol, eliminating the need for RPC callbacks. File lock state is managed by the server under a lease-based model, where failure to renew the lease may result in state release by the server.
- Client caching and delegation
- Caching resembles previous versions, with client-determined timeouts for attribute and directory caching. Delegations in NFS 4.0 allow the server to assign certain responsibilities to the client, guaranteeing specific file sharing semantics and enabling local file operations without immediate server interaction.
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