EBS

EBS volume features Here is a list of important information about EBS Volumes:

• When you create an EBS volume in an Availability Zone, it is automatically replicated within that zone to prevent data loss due to a failure of any single hardware component.
• An EBS volume can only be attached to one EC2 instance at a time.
• After you create a volume, you can attach it to any EC2 instance in the same Availability Zone
• An EBS volume is off-instance storage that can persist independently from the life of an instance. You can specify not to terminate the EBS volume when you terminate the EC2 instance during instance creation.
• EBS volumes support live configuration changes while in production which means that you can modify the volume type, volume size, and IOPS capacity without service interruptions.
• Amazon EBS encryption uses 256-bit Advanced Encryption Standard algorithms (AES-256)
• EBS Volumes offer 99.999% SLA.

Instance Store volumes

• Best performance and are directly connected to EC2
• If host fails or changes, storage is lost.
• Temporary and not resilient. Only certain EC2 types come with instance store volumes.

EBS Snapshots

• They are point in time back-ups of EBS volumes that are stored in S3
• Incremental in nature
• Only stores changes since the most recent snapshot.
• If old snapshot is deleted, blocks required to restore other snapshots are retained
• Can be used to create fully restored volumes
• Can be used to create AMIs.
• Frequent snapshots increase data durability (recommended)
  • Fsfreeze (Issue this and then start snapshot) Basically stop the Ins going to instance with attached EBS.
  • Stop instance if boot volume
• Can use cloud watch events to take snapshots
• Snapshots are crash consistent.
• In order to maintain the consistency of the snapshots
  • Flush any in memory caches to the disk
  • Stop the instances before taking the snapshot (stop the OS)
• Snapshots can be copied between regions and AZs. Part of global disaster recovery plan.
• Data Lifecycle manager - is a product/service that is used to manage snapshots. Automate the snapshot process using DLM.
• Snapshots never lose data by pruning the snapshots.

Placement Groups —————————-

• Typically used in clusters where performance is importance (low latency).
• There are 2 types of placement groups.
  • Cluster placement groups (Suggestion to AWS so that EC2 are physically close together) - Max network throuput, minimize latency
    • Using same AZ, used in cluster
    • Use EC2 that has enhanced networking.
    • Can’t do placement groups for T2 instances
  • Spread placement groups.
    • EC2 instances are not on same physical host (hardware).
    • Will spread EC2s across different hardware and may be different AZs.
    • Request to AWS to put EC2 on different location.
    • spread placement group is better for smaller deployments because each instance will be in its own partition.
    • partition placement group (PPG) can be spread across several availability zones in a region, making it a good fit for larger size deployments

EBS snapshots and encryption

• Encrypted volumes will create encrypted snapshots
• Encrypted snapshot will be encrypted with the same data encryption keys.
• If an encrypted snapshot is copied to another region, you need another key.
• When EBS volume is created from snapshot, the data copy is done over time from s3.
• Read the whole volume if you want to get all the data.