2010 04 30 firstname.lastname@example.org
Preliminary Bluearc load testing
I have performed some preliminary Bluearc load testing of
/minos/data2, which is exported from blue2:/minos/data.
This is about 67 TBytes of HDS disk.
The initial goal is to determine level at which clients
can read data without creating global slowdowns.
We are concerned about slowdowns to under 1 MByte/sec.
Global slowdowns are measured by a script running on minos25
reading a fresh 100 MB file every couple of minutes,
logging data rates in files like
Rates are plotted under
Date rates for /minos/app vary widely, probably file fragmentation.
Data rates for /minos/data2 are consistently around 60 MBytes/sec.
Major slowdowns correlate with Bluearc internal latency increases.
Normal 5 msec latencies increase to over 10 during slowdowns.
Unscheduled user loads of 50 heavy reads running on GPFarm nodes
have produced slowdowns to around 20 MB/sec, which is not severe.
Minos uses to cpn script to regulate Bluearc traffic.
The access limit is set to 20 ( April 30 2010 ),
and has been set as high as 40 for weeks, with no ill effect.
T E S T S
In recent tests, a controlled number of clients have read files
from /minos/data2, while monitoring latencies and minos25 rates.
The cpn locking script was used to control the data rates.
Reads were performed from /minos/data2 to /dev/null.
The testing script is /grid/fermiapp/minos/scripts/munch
I list the number of clients reading data files from /minos/data2,
the net rate seen by those clients, and the minos25 read rate (MB/sec)
As requested by Fermigrid/FEF,
we have no run more than 200 clients on Fermigrid nodes
That test will be scheduled during a Fermigrid downtime.
All tests involved reading 1000 files of 100 MBytes, net 100 GB.
Limit Rate Minos25 Notes
60 30 Apr 1 18:00 Fermigrid - unscheduled user load test
10 160 30 Apr 9 22:08 Fermigrid
5 200 45 ? Apr 9 10:53 Fermigrid
20 180 55 ? Apr 9 14:40 Fermigrid
100 200 22 Apr 17 15:45 minos50-53
200 200 20 Apr 17 16:21 minos50-53 and minos17-22, 60 open files seen
200 200 24 Apr 17 16:41 minos50-53 and minos17-22, 60 open files seen
200 160 21 Apr 17 17:18 minos50-53, 17-22, 200 open files, improved munch
Tests from Fermigrid worker nodes ( D0 ), to /grid/data,
monitored by minos27
Limit Rate Minoss7 Notes
20 555 40 May 4 14:40 Fermigrid D0
200 360 4 May 4 14:50 Fermigrid D0 some clients hung 40 minutes