Comparison of NFS vs. others
From Linux NFS
Here is a description comparing NFS and other similar technologies, found at this page: [1]
Contents |
CIFS
Strengths
- Huge installed client base (not just Windows),
- good, open source server implementation available (Samba!),
- token management (oplock) and referral ("dfs") semantics are a good compromise between usefulness and simplicity
- the key part of the filesystem protocol (mostly) documented, rich file open semantics map well to Windows and related OSs,
- kerberos security integration and RPC integration
- broader in scope (print, ACL, browsing etc.) than other filesystem protocols
- optional PDU signing above the RPC allowing maximal flexibility
- Unicode
- high performance
- huge amount of loosely related management/administrative function available via various DCE RPC calls
- efficient PDUs (small frame headers, less wasted bandwidth)
Weaknesses
- the extended protocol poorly documented,
- not an IETF standard
- elements of older protocol dialects still needed adding to complexity of implementations
- protocol needs addition of lock migration/recovery and support for new transport mechanisms (e.g. RDMA)
- ACL support - although useful is hard to understand
- (item j above) management/admistrative calls are proprietary
NFSv3
Strengths
- relatively simple to implement
- maps well to Unix VFS semantics (except for caching)
- protocol easy to understand by stripping file protocol to its minimum
- leverages ONC-RPC's authentication model for free, and good, security
- many non-UNIX implementations (Windows, OS/400, ...)
- Open Group standard, see http://www.opengroup.org/bookstore/catalog/c702.htm
- test suite available at http://www.opengroup.org/testing/testsuites/vsx4nfsov.htm
- SPEC server performance benchmark available at http://www.spec.org/benchmarks.html#nfs
Weaknesses
- statelessness of core protocol causes caching problems
- few Windows NFS clients installed
- Security based on Unix Userids - no security if these are spoofable
- maps poorly to Windows operating system API
- not an IETF standard (informational description published by Sun and NetApp as an informational RFC)
- relatively weak open source server implementation (at least compared to Samba and AFS) has scalability problems
- implementing many protocols needed to get CIFS equivalent e.g. lock manager, mount and port mapping protocol, SunRPC, NIS, ONC extensions (some proprietary)
- WebNFS enhancements partially implemented adding to some confusion
- No support for Unicode, UTF/8, UCS-4, etc.
NFSv4
Strengths
- IETF standards track specification
- improved recovery (lock migration)
- supports Windows file sharing semantics better than NFS v3 did
- safe file caching
- Mandates strong authentication and integrity via Kerberos and SPKM-3
- Supports rich access control model via Windows 2000-like Access Control Lists (ACLs)
Weaknesses
- few clients
- perceived lack of Microsoft interest
- the existing prototype open source implementation is tricky to integrate into current Linux kernels
- protocol is moving target (it is not quite done yet)
- too late?
- complex
DAFS
Strengths
- Addition of RDMA to NFS style protocol, (probable) high performance in clusters and server farms.
- (see NFS v4)
Weaknesses
- unproven, lack of client support, perceived competition with NFS v4
- (see NFS v4)
HTTP/WebDAV
Strengths
- official standard
- broadly implemented
- well suited to internet
- active standardization work - protocol will improve
Weaknesses
- frame headers are large (high % of frame size is wasted)
- security integration not optimal
- slow
- not a complete match to either Linux VFS or Win2K IFS API requirements
NCP(Netware)
Strengths
- NDS integration
- good match for Windows
- good installed base on older systems
Weaknesses
- Proprietary
- poorly documented
- not a standard
- complex, with lots of dialects
- future clients questionable
AFS
(DFS is related to AFS but deprecated for various reasons)
Strengths
- Kerberos 5 integration
- abstraction layer between namespace and physical location, eases maintanance expense
- excellent Linux and Windows- Client support
- aggressive client side caching with proactive cache-invalidation
Weakness
- difficult to setup
- complex, big linux kernel module for client
Coda
Strengths
- disconnected support
Weaknesses
- Lack of commercial implementations
- lack of Windows clients
- not well understood
Lustre
(help?)
Strengths
- Fully distributed.
- Excellent performance.
Weaknesses
- Poor community interaction.
- lack of clients.
GFS
(help?)
Strengths
- Fully distributed.
Weaknesses
- Needs heavy-duty, not-standardized cluster management system.
- Linux-only (?)
GPFS
Strengths
- Highly Scalable
- Data Replication
- Policy Based Storage Management
- Good performance.
- Stable, well-tested.
Weaknesses
- Commercial-only.