FAQs
- How long does it take to launch a network?
Launching ec2
instances usually takes less than a minute (however, Amazon makes
no guarantees about launch times). Getting spot instances
usually takes longer - often another minute or two but occasionally
more. Once the instances are launched, it can take a minute for
the operating system to boot. Then ompi-ppe
performs some
configuration, which usually takes a minute or less. Altogether
it
usually takes under five minutes for the entire process, but ec2
response time can vary considerably.
- What's the difference between 'master' and 'slave' ec2 instances?
Not much. The master instance has
- An ompi hostfile (/home/ec2-user/ompi-hostfile)
that lists all the instances in the network.
- A one time RSA keypair (/home/ec2/.ssh/ppe-keypair.pub)
that
makes
it
possible
for
the
master
to
access
the
slaves
via ssh; the
slaves only have the public key /home/ec2/.ssh/ppe-keypair.pub
- The AWS Management
Console shows my instances with status 'running' but the ec2-network-manager my network as
'pending' - why?
AWS's monitoring lists instances as 'running' as soon as they are
launched, typically before the operating system has finished booting.
When launching a network, the ec2-network-manager
waits for the operating system to boot and then
performs some configuration. It does not show the network's
status as 'running' until all instances are booted and configured.
- Do I need to use the gui?
At present there is no R function to create a network.
- Can I launch cloudRmpi
AMIs using the AWS Management
console?
Yes, but you'll have to set a few things up yourself, including
creating an appropriate security group and creating an ompi hostfile.
- Can I add instances to a running network?
cloudRmpi does not support this. We
usually use cc1.4large instances.
which
are
run
in
a
cluster
placement
group; instances cannot be added to a running placement group.
- What is the difference between the pv and hvm AMIs?
Amazon supports two types of virtualization: Paravirtual Machine (PV)
and Hardware Virtual Machine (HVM). Each AMIs has one (and only
one)
of these virtualization types. Only HVM AMIs can be run in
clusters. See Choosing
an
Instance
Type and Machine
Images
for more information.
- Why do I need Java? Ompi doesn't support
it.
Amazon's api for launching EC2 instances is in Java.
- How do I cut and paste in OS X?
Used cntrl-v to paste (and
command-c to cut, as usual). This is an idyiosyncracy of the
implementation of Java on the Mac.