Storage Options on AWS - S3, EBS, Instance Storage & EFS

Friends,

In this post, I want to talk to you about different storage options on AWS. AWS gives us following types of storage options. Let's understand quick difference between them first.

1. EBS: Think of it like a disc of your server. It is Block-level storage and hence most suitable for very fast read and write operations at the same time. E.g. OS, databases etc. These are connected over network to the EC2 instances (like SAN). An EBS volume can be attached to only EC2 instance at a given time. 



2. Instance Storage:This is again block level disc with your EC2 instances, but they are local on the physical host. These are non-persistent discs and hence any data on this gets lost if the instance is stopped and started. Data is not lost in case of EC2 reboot. 



3. EFS: This is available as an equivalent of NFS. You can mount an EFS to multiple EC2 instances and use like a shared disk. This currently works only with Linux isntances and not Windows.


4. Amazon S3: This is a highly available Object level storage. Objects (files) are accessed via their keys. This is suitable for storing files which can be accessed by an application via AWS APIs. Do not use this as a disc or mount it to EC2 instances. In following videos, you can learn about various features offered by S3 along with using S3 commands via #AWS #CLI



5. Glacier: This is the archival service from AWS. Instead of doing archival on tapes (on-premises), you may choose to archive to Glacier. It is cheapest form of storage. A video on Glacier is coming soon. 

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Query from KnowledgeIndia Viewers - 001

I got following questions from one of our viewers and I thought of answering it here --

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1. Can we limit versioning, Meaning to ask, versioning if enabled keeps all the modified files, can I limit it to the last 3 modifications?
ANS: You can limit it by time. E.g. that versions of last 3 days would remain there. You can move older versions to different storage classes with help Lifecycle Policies. In another case, you can write your custom Lambda function which gets invoked every time an object gets created and it could check and keep last 3 versions of that object and delete anything older.

2.When I choose s3 from the console, it doesn't allow me to choose a region from the console, Whereas after going into S3, it allows me to choose a region? why is that?
ANS: Many people have got that confusion. In case of S3, you see all your buckets (irrespective of their region) in one UI. That's why you cannot choose region at top. But, an S3 bucket belongs to one region only, hence you need to choose that when you are creating an S3 bucket.

3.What is the need to mandate versioning in cross-region replication? Any theory behind it?

ANS: Few things are done based on Engineering choices done by the product development team. I guess this is one out of them. A very good read is this page -- http://docs.aws.amazon.com/AmazonS3/latest/dev/crr-what-is-isnot-replicated.html

4.When I give a user named trinity, full S3 admin access in IAM, and then I create a bucket named Skynet only for few users, will trinity(user) still have full access over Skynet(bucket) ?
ANS: How are you ensuring that Skynet is created for few users? When you create a resource, you don't create it for a user, rather you use IAM to control which user can access that resource. In the above case Trinity has full S3 access and hence she would be able to access Skynet. But, you can explore the opportunity of denying her access at Bucket Policy level (defined at Skynet bucket).

5. After enabling cross region replication , if i delete the content in the source or destination , that deletion is not getting replicated . i can still see the file intact in my destination folder ? [In my case, though i replicated only a part of the file from the source, [replication was successful] , But when i deleted the whole source bucket, the files still where intact in my destination ?

ANS: This is the behavior shown by S3.

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