[TriLUG] Linux(RedHat) kernel question(long/involved)

[Scott Lambdin]

Do you have 10's of thousands of files (or more) in a single directory over
NFS?  That can make the NFS server get busy, for instance when a new file is
created and the NFS server must check the file name for uniqueness.   Your
fancy "beasts" may have a hash algorithm that takes care of that though, I
don't know.   See what a

time touch /path/to/nfs/bigdir/testfile
shows.

--Scott

On Wed, Oct 27, 2010 at 2:13 PM, Leslie(Pete) Boyd <lhb at hpcc.epa.gov> wrote:

>
> Hello Trilug,
>
>    I have lurked on this list for approximately 10 years and
>    have learned so much from reading it.
>
>    Now, I have a question regarding linux kernel interals.
>
>    At this site, I manage approximately 120 linux servers and
>    several SGI Altix servers as well.
>
>    Now the question:
>
>     How does the LINUX kernel handle a multiprocessor box?
>     Situation: 1 to N users are logged into the box.
>                How are the CPUs allocated to these users?
>                How will the I/O be distributed for these users?
>
>    My reason for needing this information:
>
>    We have 40 Dell R610 servers with 8 processors and 48Gb of memory.
>    Storage for this cluster consists of two 42Tbyte SATAbeast units
>    attached via two Qlogic fiber controllers with a dedicated
>    server for each controller.
>
>    The total configuration for this cluster is 40 Dell R610s, each
>    with dual quad CPUs(320 nodes) and 72Tbytes of RAW disk space.
>
>    Torque is used to queue jobs for the cluster and MPICH is used
>    to distribute the job across the nodes. The RAIDS are mounted
>    using EXT4. NFS with automounter is used to distribute the disks
>    to each of the individual servers.
>
>    Problem: When several jobs are running on the cluster, the load
>             average on the disk servers climbs above 8. Sometimes as
>             much as 12 and the performance of the running jobs
>             drops.
>
>    We are in the process of installing/configuring a lustre
>    filesystem, however; the disks will remain attached and I
>    need to solve the load problem.
>
>    Thanks in advance for your suggestions and comments.
>
> ******************
> Leslie(Pete) Boyd
> Contractor:               The rich man isn't the one who has the most,
> Vision Technoligies       but the one who needs the least.
> Senior Systems Engineer
> US EPA  Rm. E460                --- IN GOD WE TRUST --
> 919/541-1438
> ******************
>
>
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