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Hi all, i have some doubts in a situation that i fail to get an answer in Google. I have a solaris 10 nfs server and 5 centos 6.0 nfs ...
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  1. #1
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    Memory problems in NFS client server


    Hi all,

    i have some doubts in a situation that i fail to get an answer in Google.

    I have a solaris 10 nfs server and 5 centos 6.0 nfs clients.

    The problem/situation is that in the clients the free memory is "disappearing" along the time (passing to used)..and it gets free if i umount the nfs mount point. I can see also that the speed that the memory is "disappearing" is related to the use of the nfs fs (3 of the 5 servers use the nfs fs more intensively and in those it disappears faster).

    I m mounting with:
    rw,vers=4,hard,rsize=32768,wsize=32768,noac

    Kernel version:2.6.32-71.el6.x86_64 and 2.6.32-220.13.1.el6.x86_64 (i have updated in one server to check the behavior and its the same)

    and:

    rpm -aq | grep -i nfs
    nfs-utils-1.2.2-7.el6.x86_64
    nfs4-acl-tools-0.3.3-5.el6.x86_64
    nfs-utils-lib-1.1.5-1.el6.x86_64

    and in the updated server
    nfs4-acl-tools-0.3.3-5.el6.x86_64
    nfs-utils-lib-1.1.5-4.el6.x86_64
    nfs-utils-1.2.3-15.el6.x86_64

    By the way i m checking the memory with the free -m command in this line:
    ...
    -/+ buffers/cache: 480 3286
    ...
    (i did a umount/mount some time ago so now its not bad, but in couple of days it gets the opposite or worse..)


    Can someone give me some lights about this behavior?

    Thanks

  2. #2
    Linux Guru Rubberman's Avatar
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    What does the "free" command show when this happens? Bear in mind that Linux does a LOT of file system caching, so subsequent accesses to the same files (either local or nfs mounted) are MUCH faster. The "free" command will show that.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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    Well free command show:

    free -m
    total used free shared buffers cached
    Mem: 3767 1865 1902 0 197 1079
    -/+ buffers/cache: 588 3178
    Swap: 1999 0 1999


    the amount of memory used for fs cache is used where? its in buffers or cached field right?
    When i say that free space tends to 0 i m checking the second line where free = free + buffers + cache, right?
    so along the time the memory in used field will keep increasing and of course the free tends to 0, like i m checking this in the second line the used amont is really in use right? in that line if free gets to 0 i will start to have troubles right? (well probably starting to consuming swap..)

  4. #4
    Linux Guru Rubberman's Avatar
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    Quote Originally Posted by blast View Post
    Well free command show:

    free -m
    total used free shared buffers cached
    Mem: 3767 1865 1902 0 197 1079
    -/+ buffers/cache: 588 3178
    Swap: 1999 0 1999


    the amount of memory used for fs cache is used where? its in buffers or cached field right?
    When i say that free space tends to 0 i m checking the second line where free = free + buffers + cache, right?
    so along the time the memory in used field will keep increasing and of course the free tends to 0, like i m checking this in the second line the used amont is really in use right? in that line if free gets to 0 i will start to have troubles right? (well probably starting to consuming swap..)
    This shows you have 3.7GB of memory, 1.8GB is used, 1.9GB is free, none is shared, 197MB of buffer space used, and 1079 cache is used. You are not using any swap. So, the short story is that you have over half of your physical RAM available for programs as yet before the system has to start aging out buffers and cache. The +/- buffers/cache line means that 588MB of buffer/cache space has been reclaimed, and 3.1GB has been utilized. You are not in a situation to worry at this point. You can also see how much memory has been used in more detail using the "sar" command.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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