Storage Controller

Local Storage

• Local Storage Devices
  • Somewhere to store the OS or files
• Hard Drive
• USB Storage
• CD/DVD
• Tape

Storage Area Networks

LAN / WAN and now SAN

• A Storage Area Network (SAN) is not A Network Attached Storage (NAS)
  • A NAS is just a simple CPU, a little bit of RAM and typically Linux as OS.
    • NAS will communicate with disk over IP network while a SAN is a while separate network
• Fibre Channel
  • SAN uses redundant network infrastructure.
    • We have two cards, the first one is the NIC, the second one is the Host Bus Adapter (HBA) and its basically a network card for talking to storage networks. So we can have two connections come off of this server, these are basically connecting to SAN A and SAN B, separated for redundancy if there is any issue in any of them to make sure the server always have access to the Disk.
    • The disk is presented to the world by the Storage Controller (SC), which has Fiber Channel ports that connect to each of the SANs.
  • In a SAN you have two separate infrastructures, these would be Fiber Channel Switches
    • Switch A and Switch B, each server connects with each of these switches, and through the switch the server connects to the Storage Controller.
      • Companies like NetApp or EMC make basically a storage server that sits between the disks and the real server.
      • The SC is responsible for managing hundreds of different disks, even different tears of disks, which prioritizes what's the most often accessed data and saves it on a faster storage unit like an SSD.
• Host Bus Adapter
  • A dedicated network card that's used for storage.
• Fiber Channel Switching.
  • Different types of ports, fiber optic connection.

• EMC is the Storage Controller in this example.

Storage Controller

• Presents a collection of disks to users
  • Could be different types/speeds
• Caching services
  • Manage and prioritize data
• Deduplication
  • Use Checksums between two files, if hashes match, that is deduplication, so instead of writing another file to disk, we can just make a pointer to the original file that already exists. So if someone wants to modify this file, then it is then when we create an instance of that file, only available for that machine.
  • Useful in environments with hundreds of virtual desktops with similar files.
• Storage tiering
• Backup & Recovery
  • SAN does its own processes to ensure that it has its own resiliency, things like RAID.
  • Aid use with recovery functions.