Storage Provisioning and Networking - Deploying and Managing a Cloud Infrastructure - page 263

EBS volumes are placed in specific Availability Zones. Amazon EC2 is divided into
regions and Availability Zones. Each region is a separate geographic area and has
multiple, isolated locations known as Availability Zones. Each volume is automatically
replicated within the same Availability Zone. This serves as a backup to the primary
instance in the event of data loss due to hardware failure.

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In order to monitor performance, Amazon provides CloudWatch ( http://aws
.amazon.com/cloudwatch/ ) for EBS volumes. Performance metrics such as bandwidth,
throughput, latency, queue depth, and more give users insight into how the volumes
are being used. AWS CloudWatch is accessible via the AWS Management Console or
the CloudWatch API.

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Usage and Performance
Amazon EBS volumes are bound to a particular Availability Zone with sizes anywhere
between 1 GB and 1 TB. A volume can be attached to any Amazon EC2 instance in the same
Availability Zone. A volume appears as a mounted device similar to a local disk volume. The
user can then choose format the volume with any file system (OS dependent).
It must be noted that the volume can be attached to only one instance at a time. However,
many volumes can be attached to one instance. This feature can essentially be exploited to
partition data across multiple volumes for increased I/O and throughput performance. A
high-frequency transactional database can particularly benefit from such a setup.
The EBS volumes are persistent in storing updates to the data kept in the volumes. If
an instance crashes, the instance can be immediately replaced with a new instance and
the volume can be attached to the new instance. The only restriction is that the instance
and volume must both be in the same Availability Zone.
In order to increase size of the boot partitions, EBS volumes can be declared as boot
partitions for EC2 instances. The size of the boot partition can be increased up to 1 TB.
This would essentially mean that the user can bundle the instance and data altogether in
one instance.
The EBS volumes come in two configurations, standard and provisioned IOPS:
Standard IOPS The standard configuration delivers approximately 100 IOPS with a best-
effort ability to boost to hundreds of IOPS. Standard volumes are generally well suited for
boot partitions.
Provisioned IOPS Provisioned IOPS configuration is designed to deliver high performance
for I/O-intensive workloads such as databases. An IOPS rate is selected by the user during
provisioning. Amazon currently supports up to 4,000 IOPS per provisioned IOPS volume.
To utilize the full potential of provisioned IOPS volumes, EBS-optimized instances can
be launched that deliver dedicated throughput performance between the instance and
the volume of anywhere between 500 Mbps and 1,000 Mbps. Amazon claims that such
a setup is “designed to deliver within 10% of the provisioned IOPS performance 99.9%
of the time.”