EBS, ELB & ASG Flashcards
What is EBS? What are it’s limitations?
Elastic Block Storage - a network drive that u can plug into a EC2 Instance like a USB Stick when they run and saves data even after they shut down.
One EBS Volume is bound to one AZ and cannot be attached to multiple EC2 at once, but multiple EBS can be attached to one EC2. (with the exception of EBS Multi Attach)
You get billed for the provisioned capacity.
What is EBS delete on termination?
It mean that upon termination of EC2 the attached EBS will be deleted.
It is on per default on the root EBS of EC2.
How does a EBS get attached to the Machine?
On the virtual level it gets treated as a partition of the drive.
What is EBS Snapshot?
It is a backup that also allows to transfer the data between different AZs.
How does the archive of EBS Snapshots work?
Archive tier is 75% cheaper but takes between 24h and 72 hrs to restore
What is AWS Recycle bin?
After deletion of a EBS Snapshot the data gets stored for specified retention time between 1 day and 1 year
What is AMI
Amazon Machine Image - customization of an EC2 instance with our configuration allowing for better startup time as everything is already pre-packaged.
There are build for specific region but can be copied across them.
It allows for much faster bootup
Where can u get an AMI from?
- AWS provides public AMIs
- You can make your own and maintain it as well
- AMI Marketplace - somebody else made them and maintains them (potentially requires payment)
How to make AMI?
- Lauch EC2 and customize it
- Stop it (for data integrity)
- Build AMI - also creates EBS Snapshots
- Lauch it somewhere else :)
What is EC2 Image Builder?
Used to automate creation, maintainability, validation and testing of EC AMIs
What is EC Instance Store?
It’s high-performance hardware drive attached to EC2. (physical connection)
Better I/O performance
What does it mean that EC2 Instance Store is ephemeral
The Store is ephemeral (only as long as not stopped or hardware failure)
great for buffering / cache / temporary content
but if needs saving then has to be transfered to EBS
Backups and restoration is users responsibility.
What is AWS EFS?
Elastic File System, kind of a Network File System that can be mounted on 100s of EC2 at the same time.
What are benefits and restrictions of AWS EFS?
It only works with linux instances of EC2, however can be used across different AZs.
It is pretty expensive and u pay per use (no need to reserve space)
What is a EFS Mount Target?
It’s a mount access point within an AZ that allows the EC2 instances of the AZ to connect to the EFS
What is EFS IA (Infrequent Access) and how does it work?
Storage class optimized for files that are not accessed every day.
offers up to 92% lower cost compared to normal EFS.
By setting a lifecycle policy we say that after not using (reading nor writing) a file for a specific timeframe (say 60 days) file should be moved to EFS IA.
It’s not visible to a user nor system (only cost -optimization in the backend)
What are the responsibilities of AWS EC2 Storage?
AWS -> Hardware and Network, Replication
User -> Backups, Data Encryption, Risk managment
What is Amazon FSx?
High Performance file systems on AWS.
What are the FSx types?
- FSx for windows file Server (WFS) - Windows native built on WFS. Supports Windows NTFS and SMB Protocol
- FSx for Lustre - made for (HPC) Linux + cluster. Able to scale to 100s GB/s, millions of IOPS and sub-ms latencies. Data is then usually linked to an S3 Bucket.
What is vertical scalability?
Increasing size of the instance. (More RAM, Computing power etc) (scaling up/down)
What is horizontal scalability?
Increasing number of instances. This implies an distributed system. (scaling out or in)
What does high availability mean in context of AWS?
Running the application in at least 2 different AZs (Surviving a data center loss)
What does Elasiticity mean in context of AWS?
Applying auto-scaling for a system to match the load it’s receiving. (pay-per-use, match demand, optimize costs)
What does Agility mean in context of AWS?
new IT Resources are only a click away (time reduced from weeks to minutes)
What is AWS ELB?
Elastic Load Balancer, that forwards traffic to EC2 Instances downstream.
What are benefits of AWS ELB?
- Exposing single point of access (DNS)
- Allowing seamless handle of failures downstream, by doing health checks
- Provide HTTPS for the websites
- Provide High Availability thanks to multiple AZs
What are 3 kinds of ELBs offered by AWS?
- Application layer (HTTP / HTTPs only) - Layer 7
- Network Load Balancer (Ultra high performance for UDP/TCP) - Layer 4
- Gateway Load Balancer - Layer 3
What does the Application Load Balancer do?
It distributes the HTTP / HTTPs / gRPC protocols of layer 7
It has HTTP routing functions
It offers static DNS (URL)
What does Network Load Balancer do?
it works on TCP/UDP protocol of layer 4
Very high performance with millions of request per second
Offers static IP through Elastic IP
What is Gateway Load Balancer do?
It works with GENEVE Protocol on IP packets of layer 3
It manages Route Traffic to Firewalls that we maange on EC2 Instances
Offers Intrusion detection and deep paket inspection by having a special EC2 Instance that receives the pakets from GLB and analyses the incoming pakets before returning them to the GLB to be forwarded to Application
What is an Auto Scaling Group (ASG)
It automatically scales out and in depending on the traffic to ensure that we are having the minimum costs for the current load on the server without users noticing.
Also in case of the Application being unhealthy we can deregister it and start up a new one :)
How does the ASG work?
We set Desired Capacity, the minimum size and maximum.
Eg. minimum one EC2, desired 3 EC2 Instances and max 5 EC2 Instances
What ASG Strategies are there?
- Manual Scaling
- Dynamic Scaling - respond to changing demand
a) Simple / Step Scaling - when CloudWatch alarm is triggered (e.g. CPU > 70% / CPU < 30%)
b) Target Tracking Scaling - e.g Average CPU of all Instances should be around 40 %
c) Scheduled Scaling - We anticipate patterns to occur that e.g. 10 pm to 4 am on fridays we need more capacity - Predictive Scaling - uses ML based on the past traffic, automatically provisioning the correct number of instances in advance.
