On Dec 9, 2006, at 8:59 , Jim Mauro wrote:
Anyway....I'm feeling rather naive' here, but I've seen the "NFS
enforced synchronous semantics" phrase
kicked around many times as the explanation for suboptimal
performance for metadata-intensive
operations when ZFS is the underlying file system, but I never
really understood what's "unsynchronous"
about doing the same thing to a local ZFS
If I remember correctly, the difference is that NFS requires that the
operation be committed to stable storage before the return to the
client. This is definitely a heavier operation than the local case,
where the return to the caller may happen as soon as the operation is
cached. If there's a crash, the local system does not guarantee to
the caller that the operation is on disk, but NFS does.
Both guarantee consistency but NFS makes stronger guarantees of
completeness.
--Ed
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