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[LDM #GUQ-669331]: Both Radar and Satellite feeds stopped downloading abruptly



Hi John,

Steve and I logged onto 'rime' yesterday to take a look.
We setup a test set of REQUESTs to a completely unloaded
real-server backend of our idd.unidata.ucar.edu cluster
using port 80 for the traffic, and we experienced the same
or worse latencies sending the NEXRAD3, NGRID, NIMAGE and
NOTHER feeds to rime.  The Port 80 test was to see if the
problems you are seeing are specific to transfers using
port 388, and the results are that they are not.

The only thing we can think of trying on your end is
moving the LDM queue to a RAM disk.  We have seen two
instances where moving the LDM queue to RAM disk has
resulted in a dramatic drop in receipt latencies, so
the test is worth a try.  If you agree to proceed with
this test, you will need to make a RAM disk (again,
as 'root'), but you will need to make it about half
as large as your current LDM queue (e.g., 4 GB insted
of 7); change the LDM registry entries for location
and size of the LDM queue (size so that it will fit
in the RAM disk created); remake the LDM queue in the
RAM disk; and then restart your LDM.

Before creating a RAM disk (we couldn't do this as we
would need 'root' access), a simple test is in order:
run 'iotop' (needs to be run as 'root') and see if
one or more 'ldmd' processes are showing very high
use numbers.

Please let us know if you are willing to do the RAM
disk test.  Again, we could do it for you if we had
'root' credentials on 'rime'.

Comment:  quite frankly, the RAM disk test should be
understood as grasping at straws since we don't think
that the problem is local to 'rime'.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: GUQ-669331
Department: Support LDM
Priority: Normal
Status: Closed
===================
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NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.