NFS reliability? - NFS

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  1. NFS reliability?

    How reliable is NFS?

    That is, if a directory subtree (for example) is mv'ed across NFS, what's
    the likelihood that the data are not 100% preserved?

    Furthermore, does NFS include checksums to ascertain the fidelity of the
    transfer?



  2. Re: NFS reliability?

    "sinister" writes:

    >How reliable is NFS?


    About as reliable as the transport you use (so you get the usual
    ethernet CRC and UDP or TCP checksum protection). This is usually
    sufficient but those checksums do not protect against all errors;
    the best thing to do is use a flavour of secure RPC with integrity
    enabled. That will give you a secure checksum with a negligible
    chance of file corruption. (Data corruption which passes the TCP
    and UDP checksums does occur)

    >That is, if a directory subtree (for example) is mv'ed across NFS, what's
    >the likelihood that the data are not 100% preserved?


    Small but it's hard to put a finger on.

    >Furthermore, does NFS include checksums to ascertain the fidelity of the
    >transfer?


    See above.

    Casper
    --
    Expressed in this posting are my opinions. They are in no way related
    to opinions held by my employer, Sun Microsystems.
    Statements on Sun products included here are not gospel and may
    be fiction rather than truth.

  3. Re: NFS reliability?

    On Wed, 10 Nov 2004 12:49:37 +0000, Casper H. S. Dik wrote:
    > "sinister" writes:
    >>How reliable is NFS?

    >
    > About as reliable as the transport you use (so you get the usual
    > ethernet CRC and UDP or TCP checksum protection). This is usually
    > sufficient but those checksums do not protect against all errors;
    > the best thing to do is use a flavour of secure RPC with integrity
    > enabled. That will give you a secure checksum with a negligible
    > chance of file corruption. (Data corruption which passes the TCP
    > and UDP checksums does occur)
    >
    >>That is, if a directory subtree (for example) is mv'ed across NFS, what's
    >>the likelihood that the data are not 100% preserved?

    >
    > Small but it's hard to put a finger on.


    FWIW, and I will admit that this is "anecdotal" (i.e. not any kind of
    documented reproducible test case), but it might depend on the client
    and/or server platform. I could swear that I have had "stuff evaporate"
    when working on (hated word?) Linux NFS clients, accessing files on
    Solaris8 or 9 NFS servers. Typically this happens when renaming files in
    script loops, with overlaps between old and new filename ranges. I have
    gone back to carefully examine shell history and the files that were
    supposed to be there were gone. I had backups, but it was unsettling.
    It's almost as though some of the directory operations got out of sequence
    (dunno the internal details). As I say, this is just anecdotal, but maybe
    something is still busted in Linux NFS. Be careful out there. YMMV

    You don't say, but since 2 of the newsgroups you posted to are sun and
    solaris, can we assume that both client and server are Solaris machines? I
    would have more confidence in that combination. The Linux client usually
    works, too, but there have been 1 or 2 times over the last number of years...

    >>Furthermore, does NFS include checksums to ascertain the fidelity of the
    >>transfer?

    >
    > See above.
    >
    > Casper


    --
    Juhan Leemet
    Logicognosis, Inc.


  4. Re: NFS reliability?


    "Juhan Leemet" wrote in message
    newsan.2004.11.11.08.57.55.232387@logicognosis.com...
    > On Wed, 10 Nov 2004 12:49:37 +0000, Casper H. S. Dik wrote:
    >> "sinister" writes:
    >>>How reliable is NFS?

    >>
    >> About as reliable as the transport you use (so you get the usual
    >> ethernet CRC and UDP or TCP checksum protection). This is usually
    >> sufficient but those checksums do not protect against all errors;
    >> the best thing to do is use a flavour of secure RPC with integrity
    >> enabled. That will give you a secure checksum with a negligible
    >> chance of file corruption. (Data corruption which passes the TCP
    >> and UDP checksums does occur)
    >>
    >>>That is, if a directory subtree (for example) is mv'ed across NFS, what's
    >>>the likelihood that the data are not 100% preserved?

    >>
    >> Small but it's hard to put a finger on.

    >
    > FWIW, and I will admit that this is "anecdotal" (i.e. not any kind of
    > documented reproducible test case), but it might depend on the client
    > and/or server platform. I could swear that I have had "stuff evaporate"
    > when working on (hated word?) Linux NFS clients, accessing files on
    > Solaris8 or 9 NFS servers. Typically this happens when renaming files in
    > script loops, with overlaps between old and new filename ranges. I have
    > gone back to carefully examine shell history and the files that were
    > supposed to be there were gone. I had backups, but it was unsettling.
    > It's almost as though some of the directory operations got out of sequence
    > (dunno the internal details). As I say, this is just anecdotal, but maybe
    > something is still busted in Linux NFS. Be careful out there. YMMV
    >
    > You don't say, but since 2 of the newsgroups you posted to are sun and
    > solaris, can we assume that both client and server are Solaris machines? I


    Right. Two SunOs 5.9 machines.

    > would have more confidence in that combination. The Linux client usually
    > works, too, but there have been 1 or 2 times over the last number of
    > years...
    >
    >>>Furthermore, does NFS include checksums to ascertain the fidelity of the
    >>>transfer?

    >>
    >> See above.
    >>
    >> Casper

    >
    > --
    > Juhan Leemet
    > Logicognosis, Inc.
    >




  5. Re: NFS reliability?


    "Casper H.S. Dik" wrote in message
    news:41920e61$0$42417$e4fe514c@news.xs4all.nl...
    > "sinister" writes:
    >
    >>How reliable is NFS?

    >
    > About as reliable as the transport you use (so you get the usual
    > ethernet CRC and UDP or TCP checksum protection). This is usually
    > sufficient but those checksums do not protect against all errors;
    > the best thing to do is use a flavour of secure RPC with integrity
    > enabled. That will give you a secure checksum with a negligible
    > chance of file corruption. (Data corruption which passes the TCP
    > and UDP checksums does occur)
    >
    >>That is, if a directory subtree (for example) is mv'ed across NFS, what's
    >>the likelihood that the data are not 100% preserved?

    >
    > Small but it's hard to put a finger on.
    >
    >>Furthermore, does NFS include checksums to ascertain the fidelity of the
    >>transfer?

    >
    > See above.


    C---thanks for your thoughtful and detailed response.

    -S

    >
    > Casper
    > --
    > Expressed in this posting are my opinions. They are in no way related
    > to opinions held by my employer, Sun Microsystems.
    > Statements on Sun products included here are not gospel and may
    > be fiction rather than truth.




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