ENA is a custom network interface designed for high-performance networking on Amazon EC2 instances. It supports the latest networking technologies, including Scalable Network Interface (SR-IOV), which allows instances to share the same physical network interface for improved performance.
With ENA, instances can utilize up to 100 Gbps of network bandwidth, thus improving their ability to handle network-intensive tasks. Moreover, ENA provides automatic software updates and protects from sneaky packet format changes.
Here is an example to check if an instance supports ENA using AWS CLI:
aws ec2 describe-instances –instance-ids i-1234567890abcdef0 –query “Reservations[].Instances[].EnaSupport”
The return value `true` indicates that ENA is enabled for the instance; otherwise, `false` is returned.
Part 2. Instance Store
An instance store provides temporary block-level storage for EC2 instances. This storage is located on disks that are physically attached to the host computer, offering high-performance operations.
Due to its temporal nature, the data in an instance store only persists during the lifetime of its associated instance. If an instance is stopped or terminated, the data in the instance store is lost. However, the data is available through reboots, and you can back it up to Amazon S3 for persistence.
Instance stores can be beneficial for buffer, cache, scratch data, and other temporary content that applications can re-create quickly.
You can use the describe-instances command in AWS CLI to check if your instances have instance stores and their configurations:
aws ec2 describe-instances –instance-ids i-1234567890abcdef0 –query “Reservations[].Instances[].BlockDeviceMappings[]”
Part 3. Placement Groups
Placement groups are logical groupings of instances within a single Availability Zone, enabling applications to participate in a low-latency, 10 Gbps network.
There are three types of placement groups: Cluster, Spread, and Partition.
- Cluster: groups instances into a low-latency network in a single Availability Zone, suitable for high-performance computing.
- Spread: distributes instances across underlying hardware, ensuring that instances are hosted on different hardware and reducing correlated failures.
- Partition: spreads instances across logical partitions, ensuring they share the same hardware less often and reducing the impact of hardware failures.
You can create a placement group using AWS CLI and run instances in it:
aws ec2 create-placement-group –group-name my-placement-group –strategy cluster
aws ec2 run-instances –image-id ami-0abcdef1234567890 –count 1 –instance-type c5.large –placement “GroupName=my-placement-group”
In conclusion, Amazon EC2 enhanced capabilities – ENA, instance store, and placement groups – are powerful features that significantly boost performance, help to efficiently manage system resources, and ensure the reliability of your operations.
Practice Test
True or False: Using an Elastic Network Adapter (ENA) can significantly increase the network performance of an EC2 instance.
- True
- False
Answer: True.
Explanation: ENA can provide EC2 instances with high throughput and packet-per-second performance.
Which of the following are true regarding AWS EC2 instance store?
- 1) Instance store volumes cannot be stopped.
- 2) Data persists on instance store volumes across instance stop and restart events.
- 3) Instance store volumes are ideal for temporary storage.
Answer: 1 and
Explanation: Instance store volumes are ephemeral and do not preserve data through instance stop, termination, or failure.
What is the main benefit of using placement groups in AWS?
Answer: Placement groups allow for grouping of instances into a low-latency network.
Explanation: Placement groups are used to influence the placement of a group of interdependent instances to meet the needs of workloads that benefit from low network latency.
True or False: Elastic Network Adapter can only be used with certain instance types in AWS EC
- True
- False
Answer: True.
Explanation: Not all instance types support Elastic Network Adapters, and the ones that do require additional configurations.
What does placement group strategy ‘partition’ offer?
Answer: It spreads instances across logical partitions ensuring that instances in one partition do not share the same underlying hardware with instances in different partitions.
Explanation: It reduces the likelihood of correlated hardware failures for your applications.
What happens to the data in an instance store if the EC2 instance is stopped or terminated?
Answer: The data in the instance store is lost.
Explanation: Instance store only provides temporary block-level storage for instances. This data is lost if the instance is stopped or terminated.
Can you enable Elastic Network Adapter for an already running EC2 instance?
Answer: No, it cannot be enabled on an already running instance.
Explanation: ENA support should be enabled while launching an instance and can’t be enabled for a running instance.
Which placement group strategy allows you to launch multiple instance types within a single placement group in a region?
Answer: Cluster.
Explanation: The cluster strategy provides the lowest latency, and you can launch multiple instance types in a single placement group within a region.
True or False: Placement groups can span multiple Availability Zones.
- True
- False
Answer: False.
Explanation: Each placement group can exist in only one Availability Zone, but you can have multiple placement groups in separate zones.
Is it possible to change the instance type of the instances that are already in a placement group?
Answer: Yes, but the instance must be stopped and restarted.
Explanation: You can change the instance type of an instance in a placement group, but you need to stop the instance first before you can change the type.
How can you add an instance to an existing placement group?
Answer: You can specify the placement group’s name when you launch a new instance.
Explanation: Existing instances cannot be moved into a placement group. The instances have to be launched into the placement group.
Which of the following is not a type of placement groups?
- A) Cluster
- B) Spread
- C) Partition
- D) Group
Answer: D) Group.
Explanation: AWS has three types of Placement Groups: Cluster, Spread, and Partition.
True or False: Enabling Enhanced Networking on an EC2 instance requires additional charges.
- True
- False
Answer: False.
Explanation: You can enable enhanced networking features for supported instances types without any additional charges.
Which placement group strategy provides high network flow and a low latency network?
Answer: Cluster.
Explanation: Cluster placement group packs instances close together in a single Availability Zone to provide high network flow with a low latency network.
Instance stores are associated with _______ lifecycle?
Answer: The instance.
Explanation: Instance Store’s lifecycle is tied to its associated instance. When the instance terminates, all the data on the instance store is lost.
Interview Questions
What is an Elastic Network Adapter (ENA) in AWS EC2?
An Elastic Network Adapter (ENA) is a network interface for Amazon EC2 instances that allows them to process network traffic with higher throughput, lower latency, and higher packet per second performance compared to traditional network interfaces.
What is an instance store in AWS EC2?
An instance store provides temporary block-level storage for EC2 instances. This storage is located on disks that are physically attached to the host computer and is ideal for temporary storage of information that changes frequently, like buffers, caches, and scratch data.
What is a placement group in AWS?
Placement groups are a way of placing EC2 instances close together inside an availability zone. Placement groups are recommended for applications that need low network latency, high network throughput, or both.
What are the types of placement groups in AWS EC2?
There are three types of placement groups in AWS EC2: cluster, partition, and spread. Cluster groups pack instances close together inside an availability zone. Partition groups separate instances across logical partitions ensuring that instances in one partition do not share the underlying hardware with instances in different partitions. Spread Groups distribute instances across underlying hardware.
What is the primary function of Elastic Network Adapter (ENA)?
The primary function of the Elastic Network Adapter (ENA) is to provide high-performance networking capabilities for EC2 instances, including high packet per second (PPS) performance, low latencies and low jitter.
Can I enable ENA support for an already running instance in AWS?
No, you cannot enable ENA support for a running instance. It must be enabled either during the launch of an EC2 instance or you can modify the attribute of a stopped instance.
What happens to the data in an instance store if the EC2 instance it is attached to is stopped or terminated?
If an EC2 instance is stopped or terminated, the data in the instance store is lost. The data is only temporary and is not saved to EBS volumes or S3.
What are some use cases for AWS placement groups?
AWS placement groups are recommended for use cases such as Big Data applications, HPC, machine learning, financial applications, and other scenarios where network performance and low latency are critical.
Can I move an existing EC2 instance into a placement group?
No, you cannot move an existing EC2 instance into a placement group. You have to specify the placement group at the time of launching the instance. However, you can create an AMI from your existing instance, and then launch a new instance from the AMI into a placement group.
Can you have instances of different sizes in a placement group?
Yes, you can have instances of different types and sizes in a placement group. However, it is recommended to use instances of the same size for best network performance.
What prerequisites should be ensured before enabling the ENA feature on an EC2 instance?
Before enabling the ENA feature, ensure that the operating system is supported, the latest version of the AWS CLI is installed, and the instance type supports ENA.
Can multiple placement groups have the same name in the same region?
Yes, but they must be of different types. For example, you can have a spread placement group and a cluster placement group with the same name in the same region. However, two spread placement groups or two cluster placement groups in the same region can’t have the same name.
Is there a limit to the number of instances that can be launched in a placement group?
Yes, the limits vary by the type of placement group. For cluster placement groups, the limit is the total number of instances per your AWS account limit. For partition placement groups, the limit is seven partitions per group. For spread placement groups, the limit is a maximum of seven running instances per group per account per region.
What happens when an instance in a spread placement group fails?
When an instance in a spread placement group fails, its replacement is allocated to a different, distinct hardware to maintain the integrity of the spread.
Can I share AWS Placement Groups across accounts?
No, placement groups can’t be shared across accounts. They are designed to offer low-latency network performance for a group of instances within the same account.
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