My paper called A Cloud Storage Platform In The Defense Context has been accepted for the 2nd International Conference on Cloud Computing and Services Science (CLOSER 2012).

This paper discusses a cloud storage platform in the defense context. The mobile and dismounted domains of defense organizations typically use devices that are light in storage, processing and communication capabilities. This means that it is difficult to store a lot of information on these devices locally, but also that it is infeasible to rely on a central storage system that is accessible through a network. The concept of Information of Interest (IoI) is introduced to denote the information demand of a user and its devices and applications. A novel storage platform is designed and tested that uses well-known techniques such as synchronization, caching and discovery, and uses the IoI to determine the storage strategy. A sample application was created that runs on personal computers, mobile phones and tablets. Manual and automated tests were run to show that the platform behaves as expected.

The left picture shows the start-up screen, with a photograph of the actual panels and six buttons for each of the screens. The middle picture shows the production in tabular form. The red coloring is for the 10% worst production days overall, the green coloring for the 10% best days overall. The grey background is for Saturdays and Sundays. The right picture shows the temperature of the inverter and the booster. It seems that the inverter tries to keep the temperature of the booster below 50 degrees. It does something – I don’t know what yet – until the temperature reaches 40 degrees:
The application works in both portrait mode and landscape mode. The left picture shows the production for each day from installation until the current day. The right picture shows the production on a single day, with buttons to select the day:

A lot of measurements are available, such as voltage, current and power of both inputs (solar panel strings) and the grid, temperature of the inverter and its booster, etc. The most interesting graphs are shown below. The first one shows the energy produced on each day since the solar panels were installed.

The second one shows the power of a single day, from both the input (solar panel string) and the grid. There is a difference in these two readings, because the inverter is not one hundred percent efficient in transforming DC input into AC output.

The third one shows the voltage outputs of the solar panels. Although not perfectly stable, it tries to keep quite constant at about 200V.

The fourth one shows the current outputs of the solar panels. This is what matters for the production of the panels.

The fifth one shows the temperature of the inverter itself and its booster. It seems that the inverter tries to keep the temperature of the booster below 50 degrees. As soon as it hits 50 degrees, it cools down to 40 degrees and rises again.

Curt Blank has made an open source Linux program called aurora that uses this connection to get readouts from the inverter. The program is included in the Ubuntu packages since 10.04 LTS, so it is really easy to install:

sudo apt-get install aurora

The serial connection on my laptop is called /dev/ttyS0 by Linux, so this is what we use as one of the parameters. Another required parameter is the address of the inverter. Several inverters might be present in a solar installation, so an address is needed to target a specific one. Note that this is only relevant if they are linked together with RS-485 cables. In my case there is only one and the inverter has address 2.

Let’s start with the energy in the last 10 seconds:

# aurora -a 2 -j /dev/ttyS0

Energy in the last 10 seconds (Joules) :    1948.365882

More interesting is the energy produced for today, weekly, monthly, yearly and since the inverter was installed:

# aurora -a 2 -e /dev/ttyS0

Daily Energy               =       0.094 KWh
Weekly Energy              =       0.094 KWh
Monthly Energy             =      12.447 KWh
Yearly Energy              =      12.471 KWh
Total Energy               =      12.469 KWh
Partial Energy             =      12.444 KWh

There are also readings about voltage and current. To be honest, I don’t understand the input 2 readings because there is nothing connected there.

# aurora -a 2 -d /dev/ttyS0

Input 1 Voltage            =  184.667801 V
Input 1 Current            =    2.804785 A
Input 1 Power              =  517.953552 W

Input 2 Voltage            =    0.650100 V
Input 2 Current            =    1.859635 A
Input 2 Power              =    1.208949 W

Grid Voltage Reading       =  225.644196 V
Grid Current Reading       =    1.965952 A
Grid Power Reading         =  458.323853 W
Frequency Reading          =   49.991001 Hz.

DC/AC Coversion Efficiency =        88.3 %
Inverter Temperature       =   38.024002 C
Booster Temperature        =   35.868004 C

There is also a Windows program made by Power One that shows current and historical readings called Aurora Communicator. A partial screenshot is shown below with some values when the sun shines brightly (for a November day that is).

The screenshot below shows the readings for a complete day. The lower graph shows the Watts (W) produced at each timestamp and the upper graph shows the accumulated Watt hours (Wh) values.

An inverter was also installed inside the house. The inverter is made by Power One and is called Aurora Uno PVI-2000. The inverter transforms the DC from the solar panels into AC that is fed straight into the mains of our house.

Unfortunately, the last week has seen unprecedented levels of mist, which means that our energy production was far lower than expected. Ah well, enough time left as the lifetime expectancy of the panels is around 30 years, while the inverter should last around 15 years.

I’ve been tinkering with the inverter a bit and got the monitoring software working on both Windows and Linux. More about that in the next post.

Please also note that in the stop function it decommissions the node from the cluster. This is probably not what you want in production environments.

#!/bin/bash
# chkconfig: 2345 99 01
# description: Cassandra

. /etc/rc.d/init.d/functions

CASSANDRA_HOME=/opt/apache-cassandra-0.7.4
CASSANDRA_BIN=$CASSANDRA_HOME/bin/cassandra
CASSANDRA_NODETOOL=$CASSANDRA_HOME/bin/nodetool
CASSANDRA_LOG=$CASSANDRA_HOME/log/cassandra.log
CASSANDRA_PID=/var/run/cassandra.pid
CASSANDRA_LOCK=/var/lock/subsys/cassandra
PROGRAM="cassandra"

if [ ! -f $CASSANDRA_BIN ]; then
  echo "File not found: $CASSANDRA_BIN"
  exit 1
fi

RETVAL=0

start() {
  if [ -f $CASSANDRA_PID ] && checkpid `cat $CASSANDRA_PID`; then
    echo "Cassandra is already running."
    exit 0
  fi
  echo -n $"Starting $PROGRAM: "
  daemon $CASSANDRA_BIN -p $CASSANDRA_PID >> $CASSANDRA_LOG 2>&1
  usleep 500000
  RETVAL=$?
  if [ $RETVAL -eq 0 ]; then
    touch $CASSANDRA_LOCK
    echo_success
  else
    echo_failure
  fi
  echo
  return $RETVAL
}

stop() {
  if [ ! -f $CASSANDRA_PID ]; then
    echo "Cassandra is already stopped."
    exit 0
  fi
  echo -n $"Stopping $PROGRAM: "
  $CASSANDRA_NODETOOL -h 127.0.0.1 decommission
  if kill `cat $CASSANDRA_PID`; then
    RETVAL=0
    rm -f $CASSANDRA_LOCK
    echo_success
  else
    RETVAL=1
    echo_failure
  fi
  echo
  [ $RETVAL = 0 ]
}

status_fn() {
  if [ -f $CASSANDRA_PID ] && checkpid `cat $CASSANDRA_PID`; then
    echo "Cassandra is running."
    exit 0
  else
    echo "Cassandra is stopped."
    exit 1
  fi
}

case "$1" in
  start)
    start
    ;;
  stop)
    stop
    ;;
  status)
    status_fn
    ;;
  restart)
    stop
    start
    ;;
  *)
    echo $"Usage: $PROGRAM {start|stop|restart|status}"
    RETVAL=3
esac

exit $RETVAL

If all looks alright, name the script cassandra and place it in /etc/init.d/
After that run the following commands:

mkdir /opt/apache-cassandra-0.7.4/log
chmod +x /etc/init.d/cassandra
chkconfig --add cassandra
service cassandra start

Let’s say we have a file named test.txt that contains the following content:

ALICE was beginning to get
very tired of sitting by
her sister on the bank
and of having nothing to do:
once or twice she had peeped
into the book her sister was reading,
but it had no pictures or conversations in it,
"and what is the use of a book," thought Alice,
"without pictures or conversations?'

If we use grep to find lines matching “bank”, we write:

grep bank test.txt

and get:

her sister on the bank

If we want to list some line(s) before the matched line, we write:

grep -B1 bank test.txt

where the 1 denotes the number of lines to list, and get:

very tired of sitting by
her sister on the bank

If we want to list some line(s) after the matched line, we write:

grep -A2 bank test.txt

where the 2 denotes the number of lines to list, and get:

her sister on the bank
and of having nothing to do:
once or twice she had peeped

The two options can be combined as well, but I leave that as an exercise to the reader .

• Tell XenServer the template is not a default template
• Convert the template to a VM
• Delete the VM

xe template-param-set other-config:default_template=false uuid=[uuid]
xe template-param-set is-a-template=false uuid=[uuid]
xe vm-destroy uuid=[uuid]

where [uuid] is the UUID of the template you want to delete.

I presented a paper called The IETF Should Create An Intercloud RFC at the the 1st International Conference on Cloud Computing and Services Science (CLOSER 2011) conference.

This paper discusses the current state of cloud computing and shows that it is comparable to the state of networks before the internet. Clouds need to be connected more to make it easier for users to switch between providers and at the same time make it easier for providers to supply ”infinite resources”. At the moment the big cloud providers do not feel the need to standardize this intercloud and there is no authorative body that sets the standard. This paper argues that it is necessary for the IETF to take its current effort to create a cloud reference framework one step further and standardize the interfaces between the functions and layers as well.