Added SysOps notes

Author: rishabkumar7

SAA.md

@@ -107,6 +107,63 @@ Policy versioning: Customer managed policies can normally have only 5 versions b
 
 IAM Roles are more preferred instead of resource based policies which are not extendable to other entities
 
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+> **EC2:**
+
+-   When EC2 was first launched all AMI's were backed by Instance store or Ephemeral storage
+-   Ephemeral storage is non-persist or temporary storage
+-   When an instance is shut down, even if turned back up, the the contents of the instance store, or ephemeral storage will be gone, and unaccessible
+-   Stopping and restarting an instance moves the instance to another host, hence the lost data
+-   EC2 eventually got the ability to attach EBS or Elastic Block Storage which allows for data persistence
+-   There is NO way to flag data preservation on ephemeral storage, if the instance restarts, or the host experiences issues, you can incur data loss
+-   2 types of Volumes
+-   Root Volume:
+    -   This is where your operating system is installed
+    -   Can either be EBS or Ephemeral
+    -   Max size is 10GB
+    -   EBS root device volume can be up to 1 or 2TB depending on OS
+    -   Delete on Terminate is the default value
+-   Additional Volumes:
+    -   This can be your D:, E:, F: / dev/sdb, /dev/sdc, /dev/sdd etc..
+    -   Delete on Terminate is NOT the default value, additional volumes WILL persist after the instance is terminated and must be manually deleted
+ - Termination:
+    - We have an instance where shutdown behavior = terminate and enable, terminate protection is ticked
+    - We shutdown the instance from the OS, what will happen ?
+    - The instance will still be terminated!   
+
+> **EBS:**
+
+-   Allows users to have data persistence
+-   EBS volumes can be detached from an instance and attached to other instances without data loss
+-   EBS volumes can only be attached to a single instance at a time
+-   EBS root volumes are terminated/deleted by default when the EC2 instance is terminated
+-   Termination/Deletion default behavior can be stopped by un-selecting the "Delete on Termination" option when creating the instance or by setting the deleteontermination flag to false using the command line at boot time
+-   Non root EBS volumes attached to the instance are preserved if you delete the instance
+-   Boot time is quicker using EBS, typically less than 1 minute, where Instance store volumes are generally less than 5 minutes
+-   Must manually delete additional EBS volumes when an instance is terminated. Failure to do so will hold a storage charge for unattached non deleted volumes
+
+> **Placement Groups**
+
+- Sometimes you want control over the EC2 Instance placement strategy
+- That strategy can be defined using placement groups
+- When you create a placement group, you specify one of the following
+strategies for the group:
+    - Cluster---clusters instances into a low-latency group in a single Availability Zone
+    - Spread---spreads instances across underlying hardware (max 7 instances per
+    group per AZ) -- critical applications
+    - Partition---spreads instances across many different partitions (which rely on
+    different sets of racks) within an AZ. Scales to 100s of EC2 instances per group
+    (Hadoop, Cassandra, Kafka)
+
+> **EC2 Instance Launch Types**
+- On Demand Instances: short workload, predictable pricing
+- Reserved: (MINIMUM 1 year)
+    - Reserved Instances: long workloads
+    - Convertible Reserved Instances: long workloads with flexible instances
+    - Scheduled Reserved Instances: example -- every Thursday between 3 and 6 pm
+- Spot Instances: short workloads, for cheap, can lose instances (less reliable)
+- Dedicated Instances: no other customers will share your hardware
+- Dedicated Hosts: book an entire physical server, control instance placement
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 Databases