Placement

Placement

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The placement API service was introduced in the 14.0.0 Newton release withinthe nova repository and extracted to the placement repository in the 19.0.0Stein release. This is a REST API stack and data model used to track resourceprovider inventories and usages, along with different classes of resources.For example, a resource provider can be a compute node, a shared storage pool,or an IP allocation pool. The placement service tracks the inventory and usageof each provider. For example, an instance created on a compute node may be aconsumer of resources such as RAM and CPU from a compute node resourceprovider, disk from an external shared storage pool resource provider and IPaddresses from an external IP pool resource provider.

Students who plan to earn a degree or certificate at LCC, or who plan to transfer to a four-year institution, must complete placement testing or equivalent before enrolling. Many placement options available.

--> *//*-->*/Most students who are new to Lake Michigan College will be asked to demonstrate basic skills in writing, math and reading before registering for classes. This is done by submitting transcripts showing a GPA of 2.5, or qualifying ACT/SAT test scores (see chart below for qualifying scores). Otherwise, you can take a placement test at LMC.

When you launch a new EC2 instance, the EC2 service attempts to place the instance in such a way that all of your instances are spread out across underlying hardware to minimize correlated failures. You can use placement groups to influence the placement of a group of interdependent instances to meet the needs of your workload. Depending on the type of workload, you can create a placement group using one of the following placement strategies:

A cluster placement group is a logical grouping of instances within a single Availability Zone. A cluster placement group can span peered virtual private networks (VPCs) in the same Region. Instances in the same cluster placement group enjoy a higher per-flow throughput limit for TCP/IP traffic and are placed in the same high-bisection bandwidth segment of the network.

Cluster placement groups are recommended for applications that benefit from low network latency, high network throughput, or both. They are also recommended when the majority of the network traffic is between the instances in the group. To provide the lowest latency and the highest packet-per-second network performance for your placement group, choose an instance type that supports enhanced networking. For more information, see Enhanced Networking.

If you try to add more instances to the placement group later, or if you try to launch more than one instance type in the placement group, you increase your chances of getting an insufficient capacity error.

If you receive a capacity error when launching an instance in a placement group that already has running instances, stop and start all of the instances in the placement group, and try the launch again. Starting the instances may migrate them to hardware that has capacity for all of the requested instances.

Partition placement groups help reduce the likelihood of correlated hardware failures for your application. When using partition placement groups, Amazon EC2 divides each group into logical segments called partitions. Amazon EC2 ensures that each partition within a placement group has its own set of racks. Each rack has its own network and power source. No two partitions within a placement group share the same racks, allowing you to isolate the impact of hardware failure within your application.

Partition placement groups can be used to deploy large distributed and replicated workloads, such as HDFS, HBase, and Cassandra, across distinct racks. When you launch instances into a partition placement group, Amazon EC2 tries to distribute the instances evenly across the number of partitions that you specify. You can also launch instances into a specific partition to have more control over where the instances are placed.

A partition placement group can have partitions in multiple Availability Zones in the same Region. A partition placement group can have a maximum of seven partitions per Availability Zone. The number of instances that can be launched into a partition placement group is limited only by the limits of your account.

If you start or launch an instance in a partition placement group and there is insufficient unique hardware to fulfill the request, the request fails. Amazon EC2 makes more distinct hardware available over time, so you can try your request again later.

Spread placement groups are recommended for applications that have a small number of critical instances that should be kept separate from each other. Launching instances in a spread level placement group reduces the risk of simultaneous failures that might occur when instances share the same equipment. Spread level placement groups provide access to distinct hardware, and are therefore suitable for mixing instance types or launching instances over time.

If you start or launch an instance in a spread placement group and there is insufficient unique hardware to fulfill the request, the request fails. Amazon EC2 makes more distinct hardware available over time, so you can try your request again later. Placement groups can spread instances across racks or hosts. You can use host level spread placement groups only with AWS Outposts.

The following image shows seven instances in a single Availability Zone that are placed into a spread placement group. The seven instances are placed on seven different racks, each rack has its own network and power source.

A rack spread placement group can span multiple Availability Zones in the same Region. For rack spread level placement groups, you can have a maximum of seven running instances per Availability Zone per group.

Host spread level placement groups are only available with AWS Outposts. For host spread level placement groups, there are no restrictions for running instances per Outposts. For more information, see Placement groups on AWS Outposts.

On-Demand Capacity Reservation and zonal Reserved Instances provide a capacity reservation for EC2 instances in a specific Availability Zone. The capacity reservation can be used by instances in a placement group. When using a cluster placement group with capacity reservation, it is recommended that you reserve capacity within the cluster placement group. For more information, see Capacity Reservations in cluster placement groups.

Zonal Reserved Instances provide a capacity reservation for instances in a specific Availability Zone. The capacity reservation can be used by instances in a placement group. However, it is not possible to explicitly reserve capacity in a placement group using a zonal Reserved Instance.

The maximum network throughput speed of traffic between two instances in a cluster placement group is limited by the slower of the two instances. For applications with high-throughput requirements, choose an instance type with network connectivity that meets your requirements.

You can launch multiple instance types into a cluster placement group. However, this reduces the likelihood that the required capacity will be available for your launch to succeed. We recommend using the same instance type for all instances in a cluster placement group.

A partition placement group supports a maximum of seven partitions per Availability Zone. The number of instances that you can launch in a partition placement group is limited only by your account limits.

A rack spread placement group supports a maximum of seven running instances per Availability Zone. For example, in a Region with three Availability Zones, you can run a total of 21 instances in the group, with seven instances in each Availability Zone. If you try to start an eighth instance in the same Availability Zone and in the same spread placement group, the instance will not launch. If you need more than seven instances in an Availability Zone, we recommend that you use multiple spread placement groups. Using multiple spread placement groups does not provide guarantees about the spread of instances between groups, but it does help ensure the spread for each group, thus limiting the impact from certain classes of failures.

Use the create-placement-group command. The following example creates a placement group named my-cluster that uses the cluster placement strategy, and it applies a tag with a key of purpose and a value of production.

Use the create-placement-group command. Specify the --strategy parameter with the value partition, and specify the --partition-count parameter with the desired number of partitions. In this example, the partition placement group is named HDFS-Group-A and is created with five partitions.

When you tag a placement group, the instances that are launched into the placement group are not automatically tagged. You need to explicitly tag the instances that are launched into the placement group. For more information, see Add a tag when you launch an instance.

In the Summary box, under Number of instances, enter the total number of instances that you need in this placement group, because you might not be able to add instances to the placement group later.

Under Advanced details, for Placement group name, you can choose to add the instances to a new or existing placement group. If you choose a placement group with a partition strategy, for Target partition, choose the partition in which to launch the instances.

For Placement group, select the Add instance to placement group check box. If you do not see Placement group on this page, verify that you have selected an instance type that can be launched into a placement group. Otherwise, this option is not available.

Use the run-instances command and specify the placement group name and partition using the --placement "GroupName = HDFS-Group-A, PartitionNumber = 3" parameter. In this example, the placement group is named HDFS-Group-A and the partition number is 3. 781b155fdc