Network Storage

Question 1

NAS vs. SAN

Answer 1

• Network Attached Storage (NAS)
  
  • Connect to a shared storage device across the network
  • File-level access
• Storage Area Network (SAN)
  
  • Looks and feels like a local storage device
  • Block-level access
  • Very efficient reading and writing

• Requires a lot of bandwidth
• May use an isolated network and
high-speed network technologies

Question 2

Jumbo frames

Answer 2

• Ethernet frames with more
than 1,500 bytes of payload
• Up to 9,216 bytes (9,000 is the accepted norm)

• Increases transfer efficiency
  
  • Per-packet size
  • Fewer packets to switch/route
• Ethernet devices must support jumbo frames
  
  • Switches, interface cards
  • Not all devices are compatible with others

Question 3

Fibre Channel (FC)

Answer 3

• A specialized high-speed topology
  
  • Connect servers to storage
  • 2-, 4-, 8- and 16-gigabit per second rates
  • Supported over both fiber and copper

• Servers and storage connect to a Fibre Channel switch
• Server (initiator) needs a FC interface
• Storage (target) is commonly referenced by
SCSI, SAS, or SATA commands

Question 4

Fibre Channel over the data network

Answer 4

• Fibre Channel over Ethernet (FCoE)
• Use Fibre Channel over an Ethernet network
• No special networking hardware needed
• Usually integrates with an existing Fibre Channel
infrastructure
• Not routable

• Fibre Channel over IP (FCIP)
  • Encapsulate Fibre Channel data into IP packets
  • Fibre Channel tunneling
  • Geographically separate
the servers from the storage

Question 5

iSCSI

Answer 5

• Internet Small Computer Systems Interface
  
  • Send SCSI commands over an IP network
  • Created by IBM and Cisco, now an RFC standard
• Makes a remote disk look and operate like a local disk
  
  • Like Fibre Channel
• Can be managed quite well in software
  
  • Drivers available for many operating systems
  • No proprietary topologies or hardware needed

Question 6

InfiniBand

Answer 6

• High-speed switching topology
  
  • Alternative to Fibre Channel
• Copper and Fiber options
  
  • QSFP connectors

• Popular use in research and supercomputers
• Designed for high speeds and low latency
• 100 Gbit/sec and 200 Gbit/sec speeds are common
• Links can be aggregated for higher
throughputs (4x, 8x, 12x links)