AWS Certified Solutions Architect Study Guide. David Higby Clinton

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      Applied properly, tags can improve the visibility of your resources, making it much easier to manage them effectively, audit and control costs and billing trends, and avoid costly errors.

      Service Limits

      By default, each AWS account has limits to the number of instances of a particular service you're able to launch. Sometimes those limits apply to a single region within an account, and others are global. As examples, you're allowed only five VPCs per region and 5,000 Secure Shell (SSH) key pairs across your account. If necessary, you can ask AWS to raise your ceiling for a particular service.

You can find up‐to‐date details regarding the limits of all AWS services at docs.aws.amazon.com/general/latest/gr/aws_service:limits.html.

EC2 Storage Volumes

      Storage drives (or volumes as they're described in AWS documentation) are for the most part virtualized spaces carved out of larger physical drives. To the OS running on your instance, though, all AWS volumes will present themselves exactly as though they were normal physical drives. But there's actually more than one kind of AWS volume, and it's important to understand how each type works.

      Elastic Block Store Volumes

      You can attach as many Elastic Block Store (EBS) volumes to your instance as you like (although one volume can be attached to no more than a single instance at a time) and use them just as you would hard drives, flash drives, or USB drives with your physical server. And as with physical drives, the type of EBS volume you choose will have an impact on both performance and cost.

      The AWS SLA guarantees the reliability of the data you store on its EBS volumes (promising at least 99.99 percent availability), so you don't have to worry about failure. When an EBS drive does fail, its data has already been duplicated and will probably be brought back online before anyone notices a problem. So, practically, the only thing that should concern you is how quickly and efficiently you can access your data.

      There are currently four EBS volume types, two using SSD technologies and two using the older spinning hard drives. The performance of each volume type is measured in maximum IOPS/volume (where IOPS means input/output operations per second).

      EBS‐Provisioned IOPS SSD

      If your applications will require intense rates of I/O operations, then you should consider provisioned IOPS, which provides a maximum IOPS/volume of 64,000 and a maximum throughput/volume of 1,000 MB/s. Provisioned IOPS—which in some contexts is referred to as EBS Optimized—can cost $0.125/GB/month in addition to $0.065/provisioned IOPS.

      EBS General‐Purpose SSD

      For most regular server workloads that, ideally, deliver low‐latency performance, general‐purpose SSDs will work well. You'll get a maximum of 16,000 IOPS/volume, and it will cost you $0.10/GB/month. For reference, a general‐purpose SSD used as a typical 8 GB boot drive for a Linux instance would, at current rates, cost you $9.60/year.

      Throughput‐Optimized HDD

      Throughput‐optimized HDD volumes can provide reduced costs with acceptable performance where you're looking for throughput‐intensive workloads, including log processing and big data operations. These volumes can deliver only 500 IOPS/volume but with a 500 MB/s maximum throughput/volume, and they'll cost you only $0.045/GB/month.

      Cold HDD

      When you're working with larger volumes of data that require only infrequent access, a 250 IOPS/volume type might meet your needs for only $0.025/GB/month.

Table 2.4 lets you compare the basic specifications and estimated costs of those types.

TABLE 2.4 Sample costs for each of the four EBS storage volume types

	EBS‐provisioned IOPS SSD	EBS general‐purpose SSD	Throughput‐optimized HDD	Cold HDD
Volume size	4 GB–16 TB	1 GB–16 TB	500 GB–16 TB	500 GB–16 TB
Max IOPS/volume	64,000	16,000	500	250
Max throughput/volume (MB/s)	1,000	250	500	250
Price (/month)	$0.125/GB + $0.065/prov IOPS	$0.10/GB	$0.045/GB	$0.025/GB

      EBS Volume Features

      All EBS volumes can be copied by creating a snapshot. Existing snapshots can be used to generate other volumes that can be shared and/or attached to other instances or converted to images from which AMIs can be made. You can also generate an AMI image directly from a running instance‐attached EBS volume—although, to be sure no data is lost, you should shut down the instance first.

      EBS volumes can be encrypted to protect their data while at rest or as it's sent back and forth to the EC2 host instance. EBS can manage the encryption keys automatically behind the scenes or use keys that you provide through the AWS Key Management Service (KMS).

Exercise 2.4 will walk you through launching a new instance based on an existing snapshot image.

EXERCISE 2.4

      Create and Launch an AMI Based on an Existing Instance Storage Volume

      1 If necessary, launch an instance and make at least some token change to the root volume. This could be something as simple as typing touch test.txt on a Linux instance to create an empty file.

      2 Create an image from the instance's volume (you'll access the dialog through the Actions pull‐down menu in the Instance's Dashboard).

      3 Launch an instance from the console and select the new AMI from the My AMIs tab.

      4 Log into the instance and confirm that your