Elastic Compute Cloud (EC2) Basics Flashcards

Question

AMI Lifecycle

Answer 1

1. Launch = You use an AMI to launch an EC2 instance 2. Configure = You can take the instance, that you provisioned during the "Launch" phase, and then you can apply some configuration, to bring your instance into a state where it's perfectly set up for your organization. 3. Create Image = You can take that configured instance, and actually create your own AMI. This AMI will contain a few things: When you create an AMI for any EBS volumes, which are attached to that EC2 instance, we have EBS Snapshots created from those volumes (Incremental but first one is a full copy, of all the data that's used on that EBS volume). When you make an AMI, the EBS Snapshots are taken, and those Snapshots are actually referenced inside the AMI, using a "Block device mapping". -Block Device Mapping = Is just a table of data, it links the Snapshots ID, and it has, for each one of those Snapshots, a device ID that the original volumes had on the EC2 instance. BDM will contain the ID of the right Snapshot, and the Block Device of the original volume (/dev/xvda) 4. Launch = When this AMI is used to create a new instance, this instance will have the same EBS volume configuration as the original. When you launch an instance using an AMI, what actually happens is the Snapshots are used to create new EBS volumes in the AZ, that you're launching that instance into, and those volumes are attached to that new instance, using the same Device ID.

Answer 2

-AMI = One Region, only works in that one region. -AMI Baking - creating an AMI from a configured instance + application -An AMI CAN'T BE EDITED - launch instance, update configuration and make a new AMI -AMIs can be copied between regions (includes its Snapshots) -Permissions - default = your account -AMI costs, are the storage capacity used, by the EBS Snapshots that the AMI references.

Answer 3

Instances of different sizes run on the same EC2 hosts - consuming a defined allocation of resources -On-demand instances are isolated but multiple customer instances run on shared hardware -Per-second billing while instance is running. Associated resources such as storage consume capacity, so bill, regardless of instance state. -Default purchase option - No interruption, No capacity reservation, Predictable pricing, no upfront cost, no discount. -Short term workloads - Unknown Workloads - Apps which can't be interrupted

Answer 4

-SPOT pricing is AWS selling UNUSED EC2 host capacity for up for UP TO 90% discount - the spot price is based on the SPARE CAPACITY AT A GIVEN TIME. -NOT RELIABLE (ONLY short-term) -NEVER USE SPOT for workloads which CAN'T TOLERATE INTERRUPTIONS -Non-time critical - Anything which can be rerun, Bursty Capacity needs, Cost sensitive workloads, Anything which is stateless

Answer 5

Reservations are a way you commit to AWS, that you will use resourcesfor a length of time. They form a part of most larger deployments within AWS. -LONG-TERM CONSISTENT usage of EC2 -Matching instance, reduced or no p/sec price - As long as the reservation matches the instance, it will apply to that instance -Unused reservation STILL BILLED -Partial coverage of larger instance - if you provision a larger instance than the reservated capacity, it will have a partial effect, you would get a discount of a partial component of that larger instance -You can commit to 1 year (+) or 3 year terms (++) - You pay for the entire term -No-upfront - offers the least discount -Partial-Upfront - When you pay a smaller lump sum in advance, in exchance for reduced p/sec fee -All-upfront - No p/sec fee and Greatest discount (with 3y term)

Answer 6

-Is a commitment, you specify the frequency, the duration and the time -Ideal for long-term usage which doesn't run constantly - Batch Processing daily for 5 hours starting at 23:00 -You reserve the capacity for a slightly cheaper rate versus on-demand, but you can only use that capacity during that time window. -Weekly data, sales analysis, every Friday for 24 hours or you might have a larger analysis process which needs 100 hours of EC2 capacity per month -It doesn't support all instance, types or Regions -You need to purchase a minimum of 1200 hours per year - 1 year minimum

Answer 7

AWS also offers discounted hourly rates in exchange for an upfront fee and term contract. Services such as Amazon EC2 and Amazon RDS use this approach to sell reserved capacity for hourly use of Reserved Instances. When you reserve capacity with Reserved Instances, your hourly usage is calculated at a discounted rate for instances of the same usage type in the same Availability Zone (AZ). When you launch additional instances of the same instance type in the same Availability Zone and exceed the number of instances in your reservation, AWS averages the rates of the Reserved Instances and the On-Demand Instances to give you a blended rate. -Regional Reservation provides a billing discount for validinstances launched in any AZ in that region While flexible they DON'T RESERVE CAPACITY within an AZ - which is risky during major faults when capacity can be limited. When you are launching instances, even having Regional Reservation, you're launching them with the same priority as on-demand instances. -Zonal Reservation only apply to one AZ, providing billing discounts and capacity reservation in that AZ. If you launch instances into another availability zone in that Region, you get neither benefit (Full Price & No Capacity Reservation) -On-Demand capacity reservations can be booked to ensure you always have access to capacity in an AZ when you need it - but at full on-demand price. No term limits- but you pay regardless of if you consume it. Capacity Reservations don't have the same 1 or 3 year commitment requirements that you need for Reserved Instances. You're not getting any billing benefit, when using Capacity Reservations, you're just reserving the capacity. So at any point you can book a Capacity Reservations. If you know you need some EC2 capacity without worrying about the 1 or 3 year term commitments, but you don't benefit from any cost reduction.

Answer 8

Is an EC2 host, which is allocated to you IN ITS ENTIRETY. -You pay for the host itself, which is designed for a specific family of instances (No instance charges) You can launch various different sizes of instances on the host, consuming all the way up to the complete resource capacity of that host. You need to manage this capacity, if the Dedicated Host run out of capacity, then you can't launch any additional instances. -These hosts come with all the resources that you would expect from a physical machine. (number of cores, memory, local storage and network connectivity) -You would use this option, if you have Licensing based on Sockets/Cores ** Licensing it based on the amount of resources in a physical machine, not the resources that are allocated to a virtual machine or an instance within AWS -Have a feature, called Host Afinity which links instances to certain EC2 hosts So if you stop and start the instance, it remains on the same host. -Only your instances will run on Dedicated Hosts

Answer 9

Your instances run with others instances of yours and no other customers use the same hardware -You don't own, or share the host -Charges for instances but dedicated hardware -You pay a one-off hourly fee, for any Regions where you're using Dedicated Instances. -Fee for using Dedicated Instances themselves -Are common on sectors of the industry, where you have really strict requirements, which mean that you can't share infrastructure

Answer 10

Instead of focusing on a particular type of instance, in an AZ or Region. -You are making a Hourly commitment for a 1 or 3 year term. -Products have an On-demand rate and a Savings Plan rate. -Resources usage consumes Savings Plan commitment at the reduced Savings Plan rate. -Beyond your commitment... On-demand is used. Saving Plans come in two types: -Compute Savings Plan --Make an hourly spend commitment for 1 or 3 year term. --Automatically and simultaneously apply to any eligible Amazon EC2, Fargate, and Lambda usage across all supported AWS Regions up to the hourly commitment. --Save up to 66% compared to On-demand pricing. -EC2 Instance Savings Plans --Make an hourly spend commitment to an instance family and Region for 1 or 3 year term --Any instance size - Any AZ - Any O.S - Any tenancy --Automatically and simultaneously apply to eligible Amazon EC2 usage up to the hourly commitment --Save up to 72% compared to On-demand pricing.

Answer 11

Every instance within EC2 has two high level per instance status checks. Each of the two checks represents a separate set of tests, and so a failure of either of them suggests a different set of underlying problems. 1st - System Status. A failure of this check, could indicate one of few major problems: -Loss of system power -Loss of network connectivity -Host software issues -Host hardware issues This check is focused on issues impacting the EC2 service or the EC2 Host. 2nd - Instance Status. A failure of this check, could indicate one of few major problems: -Corrupted file system -Incorrect Instance Networking -OS Kernel Issues EC2 comes with a feature allowing you to recover automatically to any system check issues. You can ask the EC2 stop a failed instance, reboot it, terminate it, or you can ask EC2 to perform Auto Recovery. Auto Recovery moves the instance to a new host, starts it up with exactly the same configuration as before. So all IP Addressing is maintaned, and if software on the instance is set to Auto Start, this process could mean that the instance, as the name suggests, automatically recovers fully from any failed status check issues. -Only works on instances with EBS volumes, not using Instance Store.

Answer 12

These are two different ways that a system can scale to handle increasing, or in some cases descreasing load placed on that system. Scaling is what happens when systems need to grow or shrink in responses to increases or decreases of load placed upon them by your customers. (adding or removing resources to a system) -Vertical Scaling A "vertically scalable" system, which is constrained to running its processes on only one computer; in such systems the only way to increase performance is to add more resources into one computer in the form of faster (or more) CPUs, memory or storage. In this case, you're just resizing the EC2 instance when you scale. NEGATIVES --Each resize requires a reboot - Customer DISRUPTION - This means you can only scale generally during pre-agreed times, so within outage windows. --Larger instances often carry a $ premium --There is an upper cap on performance - Instance Size POSSITIVE --No application modification required - If an application can run on an instance then it can run on a bigger instance --Works for ALL applications - even Monoliths -Horizontal scaling A "horizontally scalable" system is one that can increase capacity by adding more computers to the system. Horizontally scalable systems are oftentimes able to outperform vertically scalable systems by enabling parallel execution of workloads and distributing those across many different computers. --Sessions are everything When you log into an application, think about Email. The state of your interaction with that application is called a "session". With a single application running on a single server, the sessions of all customers are generally stored on that server. With Horizontal Scaling, this won't work. Without changes, everytime you move between instances for a horizontally scaled application, you would have a different session or no session. You would be logged out. With Horizontal Scaling, you can be shifting between instances constantly. --Requires application support OR off-host sessions If you use off-host sessions then your session data is stored in another place, an external database. This means that the servers are "Stateless", they're just dumb instances of your application. --No disruption while scaling - Customers connections remain unaffected. --Scaling IN = removing instances / Scaling OUT = adding instances --No real limits to scaling - you can just keep adding instances --Often less expensive - no large instance premium --It can allow you to be more granular

Answer 13

-EC2 service provides data to Instances Is data about the instance that can be used to configure or manage a running instance. Is a way the instance or anything running inside the instance, can access information about the environment that it wouldn't be able access otherwise. -Accessible inside ALL instance -To access the Metadata of the Instance = http://169.254.159.254/latest/meta-data/ ** -Environment - Allows anything on the instance to query it for information about that instance, that information is divided into categories (Host name, events, Security Groups...) all information about the environment that the instance it's in. -Access to Networking information -Access to Authentication information -It's used by AWS to pass in temporary SSH keys for Instance Connect -It's used to grant access to User-Data - A way to make the instance run scriptsot perform automatic configuration steps -NOT AUTHENTICATED or ENCRYPTED **