Elastic File System -- in short is EFS
EFS is a service you need to know at a high level going into the exam .
EFS 是个考试重点
It is a managed NFS(network file system) that can be mounted on many EC2 across many different availability zones（AZ）
EFS 可以被挂载到不同的AZ 上的EC2上
High difference with EBS(it works in single AZ)
High available,scalable expensive (3xgp2) ,pay per use .
价格高，按使用量付费
But it may actually be cheaper to use EFS than EBS base on how well you use your data set .
实际上，它可以更便宜，取决你如何管理你的数据。
Use Cases
content managment web serving , data sharing , wordpress .
use NFS v4.1 protocol
uses secruity group to control access to EFS
capatible with linux base AMI (not support windows )
posix file system , so has standard API to use
scales automatically , pay per-use no capacity planning
Performance & storage classes
EFS scale
1000s of concurrent NFS client 10GB+/s throught , grow to petabyte -scale
Performance mode
general purpose (web server CMS ect... )
max I/o higth latency throughtput , parallel (big data ,media process)
Throughtput mode
bursing (1TB = 50MiB/s + burst of up to 100MiB/s)
provision: set throughtput regardless of storage . ex 1GiB/s for 1TB storage --考点
provision 可预设
storage tier (move file after N days )
standard : for frequently accessed files
infrequent access : cost to retrieve files lower price to store
EBS vs EFS
EBS volumes
can be attached to only one instance at a time
are locked in AZ
gp2 Io increases if the disk size increases
io1 can increate io independently
To migrate an EBS volume across AZ
take a shapshot
restore the shapshot to another AZ
EBS backup use IO and you should n't run them while your application is handling a lot traffic --backup 会占用IO，业务忙时不要用
Root EBS volume of instance get terminated by default if the EC2 is terminated (you can disable it )
EFS volumes
mounting 100s of instances across AZ
share web files (WordPress)
only for linux (posix)
EFS has a higher price point than EBS
can leverage EFS-IA for cost saving