Asterios Katsifodimos wrote:
> I want to increase the amount of the maximum concurrent
> connections-clients that our storage element(DPM_mysql) can handle.
This was recently discussed on [log in to unmask],
the list to use for questions related to DPM.
Ronald Starink wrote:
> Hi all,
>
> Just sharing an experience that helped to improve the performance of one
> of our DPM disk servers. Perhaps this is useful for other sites too.
>
> Recently, one of our users managed to get the load on a DPM disk server
> above 200. Although the server was still accessible, its performance was
> gone. The user initially used direct gridftp transfers to the DPM head
> node, but later tried lcg-cr/lcg-cp to access the data. Both mechanisms
> caused a high load because of the large number of concurrent transactions.
>
> After some searching we found an option to limit the number of
> connections to the gridftp server. Creating a file
> $GLOBUS_LOCATION/etc/gridftp.conf or /etc/grid-security/gridftp.conf
> containing a line
>
> connections_max 32
>
> limits the number of simultaneous gridftp connections to 32. If this
> number if connections is reached, any new connections will (temporarily)
> fail with error code
>
> 421 Service not available, closing control connection
>
> The lcg-tools correctly deal with this error. Please note, that such
> file should be present on the DPM head node to limit direct gridftp
> connections, as well as on the disk servers to restrict connections via
> lcg-*. Don't forget to restart dpm-gsiftp after changing the file.
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