Chapter 9. Storing data on hard drives: EBS and instance store

 

This chapter covers

  • Attaching persistent storage volumes to EC2 instance
  • Using temporary storage attached to the host system
  • Backing up volumes
  • Testing and tweaking volume performance
  • Differences between persistent (EBS) and temporary volumes (instance store)

Imagine your task is to migrate an enterprise application from being hosted on-premises to AWS. Typically, legacy applications read and write files from a file system. Switching to object storage, as described in the previous chapter, is therefore not possible. Fortunately, AWS offers good old block-level storage as well, allowing you to migrate your legacy application without the need for expensive modifications.

Block-level storage with a disk file system (FAT32, NTFS, ext3, ext4, XFS, and so on) can be used to store files as you would on a personal computer. A block is a sequence of bytes, and the smallest addressable unit. The OS is the intermediary between the application that wants to access files and the underlying file system and block-level storage. The disk file system manages where (at what block address) your files are stored. You can use block-level storage only in combination with an EC2 instance where the OS is running.

The OS provides access to block-level storage via open, write, and read system calls. The simplified flow of a read request goes like this:

1.  An application wants to read the file /path/to/file.txt and makes a read system call.

9.1. Elastic Block Store (EBS): Persistent block-level storage attache- ed over the network

 
 
 

9.2. Instance store: Temporary block-level storage

 
 

Summary

 
 
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