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Jason McCreary
Asked: 2013-03-23 11:26:57 +0800 CST

Where's my ephemeral storage for EC2 Instance

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I have looked through the following questions, notably How to use "Instance Store Volumes" storage in Amazon EC2?

However, it didn't answer. I created a EC2 small instance with EBS as the root device. The AWS instance types list an "instance store" of 160GB. But where is it?

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/xvda1            7.9G  3.6G  4.3G  46% /
tmpfs                 1.9G     0  1.9G   0% /dev/shm

$ mount
/dev/xvda1 on / type ext4 (rw,noatime)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)

So how to find the empheral store (160GB) and use it.

Note: I am aware of the difference between ephemeral and elastic stores. I need this space for use temporary, transient data used by the application to help with disk I/O between EBS.

UPDATE

Requested output per comments:

$ fdisk -l
Disk /dev/xvda1: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

$ cat /proc/partitions
major minor  #blocks  name

 202        1    8388608 xvda1
amazon-ec2

1 Answers

  1. Best Answer

    RTFM - I found my answer in the Amazon EC2 Instance Store docs.

    Instances that use Amazon EBS for the root device do not, by default, have instance store available at boot time. Also, you can't attach instance store volumes after you've launched an instance. Therefore, if you want your Amazon EBS-backed instance to use instance store volumes, you must specify them using a block device mapping when you create your AMI or launch your instance. Examples of block device mapping entries are: /dev/sdb=ephemeral0 and /dev/sdc=ephemeral1.

    So in my case, since I choose an EBS root device, I'll need to rebuild the instance with the instance store volume.

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