[ubuntu-cloud] root volume of cluster compute instance

Eric Hammond ehammond at thinksome.com
Wed Jun 1 00:57:33 UTC 2011


The default 8 GB (not 10 GB) on that AMI belongs to the root disk which
is stored on an EBS volume.

The 1690 GB storage Amazon says is available to cc1.4xlarge is primarily
comprised of two 840 GB ephemeral store drives.  (If you notice that
this does not quite add up, it's because they count 10GB for the root
partition which is the default on older AMIs.)

The Alestic.com articles you reference talk about changing the size of
the EBS root disk.  This can go up to 1,000 GB (1TB).

If you follow those instructions, you will be paying some extra for the
root disk storage and the disk IO since it is EBS.  Ephemeral storage
and its IO are free, but are more, um, ephemeral.

EBS volumes can persist through stop/start of an instance and even (if
properly configured) past the termination of an instance.  Ephemeral
storage disappears forever as soon as an instance is stopped or
terminated (or instance hardware failure) with no hope of recovery.

EBS and ephemeral storage have slightly different performance
characteristics, but that's the topic of many long discussions and AWS
posts with different conclusions from each.

Now, you'll still be wondering how to access the ephemeral storage you
were promised.  Turns out there is a bug in Ubuntu on EC2 which prevents
these from being mounted with the cluster compute instances:


Unfortunately, this bug has recently moved to "expired" and I'm not sure
how one would bring it back into the attention of the powers that be
(though they're probably reading this list).

Eric Hammond

On 05/31/2011 05:31 PM, Jonathan Marston wrote:
> Hello,
> I just fired up an ubuntu 11.04 cluster compute instance (
> ebs-hvm-cluster, ami-1cad5275 )
> It looks great, fires up fine, but the root partition is only 10gb. Here
> is what df -h returns
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sda1             7.9G  2.5G  5.1G  33% /
> none                   12G  140K   12G   1% /dev
> none                   12G   88K   12G   1% /dev/shm
> none                   12G   96K   12G   1% /var/run
> none                   12G     0   12G   0% /var/lock
> The cc1.4xlarge is supposed to have 1690gb of space available to it
> which I would like to make available. T
> I had read these two very useful blog posts by Eric Hammond but wasn't
> able to get it to work. The resize2fs command returns the following:
> "The filesystem is already 2094474 blocks long.  Nothing to do!"
> http://alestic.com/2009/12/ec2-ebs-boot-resize
> http://alestic.com/2010/02/ec2-resize-running-ebs-root
> Any advice on how I can make the full storage space available? 
> Jon Marston
> EnglishCentral

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