Information Technology Reference
In-Depth Information
A user can interact with EC2 using a set of SOAP messages and can list
available AMIs, boot an instance from an image, terminate an image, display
the running instances of a user, display console output, and so on. The user
has root access to each instance in the elastic and secure computing environ-
ment of EC2. The instances can be placed in multiple locations in different
regions and availability zones.
EC2 allows the import of virtual machine images from the user environ-
ment to an instance through a facility called VM import. It also automati-
cally distributes the incoming application traffic among multiple instances
using the elastic load-balancing facility. EC2 associates an elastic IP address
with an account; this mechanism allows a user to mask the failure of an
instance and remap a public IP address to any instance of the account with-
out the need to interact with the software support team.
16.1.1.2 Simple Storage Service (S3)
Simple storage service (S3) is a storage service designed to store large objects.
It supports a minimal set of functions: write, read, and delete. S3 allows an
application to handle an unlimited number of objects ranging in size from
1 byte to 5 TB. An object is stored in a bucket and retrieved via a unique
developer-assigned key. A bucket can be stored in a region selected by the
user. S3 maintains the name, modification time, an access control list, and up
to 4 kB of user-defined metadata for each object. The object names are global.
Authentication mechanisms ensure that data are kept secure; objects can be
made public, and rights can be granted to other users.
S3 supports PUT, GET, and DELETE primitives to manipulate objects but
does not support primitives to copy, rename, or move an object from one
bucket to another. Appending to an object requires a read followed by a
write of the entire object.
16.1.1.3 Elastic Block Store (EBS)
EBS provides persistent block-level storage volumes for use with Amazon EC2
instances. A volume appears to an application as a raw, unformatted, and reli-
able physical disk; the size of the storage volumes ranges from 1 GB to 1 TB.
The volumes are grouped together in availability zones and are automatically
replicated in each zone. An EC2 instance may mount multiple volumes, but a
volume cannot be shared among multiple instances. The EBS supports the cre-
ation of snapshots of the volumes attached to an instance and then uses them
to restart an instance. The storage strategy provided by EBS is suitable for
database applications, file systems, and applications using raw data devices.
It is important to mention that an EBS volume can only be mounted to one
single instance, which, in turn, must be located in the same availability zone.
An EBS volume implements persistent storage, that is, it preserves the data
after termination of the instance.
Search WWH ::




Custom Search