SAN Protocols

SAN Protocols

SAN is the most common storage networking technology. Now a days all business-critical applications run by enterprises prefer SAN only to achieve high throughput and low latency. Flash storage is rapidly growing in case of deployments due to its high performance. As in previous post we have known a little understanding about the SAN and NAS. Here we will have another little basic on the SAN protocols.  The common SAN protocols are FCP, iSCSI, FCoE, FC-NVMe. Lets have a overview of them to know more. 

FCP Overview

FCP or Fibre Channel Protocol used as SAN or block protocol. It uses fibre channel transport protocols. Mostly used protocol in case of largest deployments. It uses dedicated adapters, cables, and switches, and it's different from ethernet at all layers of the OSI layer up to the physical layer level. It uses cards which are called HBAs, host bus adapters, and they look very like normal ethernet network cards but they're different. And it uses switches across the network, but we use fibre channel switches, they look like ethernet switches, but they are different. Fibre channel is different than ethernet at every level. It supports bandwidths of from 1- 128 GB per second and sends SCSI commands over the fibre channel. 

iSCSI overview

It stands for the Internet Small Computer System Interface protocol. iSCSI encapsulates SCSI commands inside an Ethernet frame and then uses an IP Ethernet network for transport. It runs over Ethernet networks, and it was a less expensive alternative to Fibre Channel. The SAN Fibre Channel was expensive due to its own dedicated infrastructure and only accepted hardware types. Then iSCSI was developed to be a less expensive alternative running over standard Ethernet networks. It is a popular SAN technology and it runs over Ethernet, rather than Fibre Channel, it can share the data network or have its own dedicated network infrastructure. For normal storage performance, presently network cards or faster network cards were being used that makes more feasible to run iSCSI over a shared network. 

iSCSI shares a lot of the same characteristics as of Fibre Channel. It uses IQNs for the addressing. IQN is known as iSCSI Qualified Names. We can alternatively use the EUI (Extended Unique Identifier). Those are both two alternative ways of doing addressing in iSCSI. IQN is used more commonly. The IQN can be up to 255 characters long. iSCSI runs over standard Ethernet, so individual ports in the host are addressed by IP addresses, as like a normal Ethernet network. 

FCoE

Known as Fibre Channel over Ethernet It is same as iSCSI protocol and it encapsulates an FC frame inside an Ethernet datagram. Like iSCSI, it uses an IP Ethernet network for transport.

FC-NVMe

Known as Non-Volatile Memory Express over Fibre Channel which is block level access protocol. It is a newer technology that uses faster PCI express bus and allows to release with best performance of  SSDs. NVMe, SAS and SATA are not compatible with each other, that means they can not be fitted in same drive. so you can fit SAS and SATA drives in the same drive bay, but the NVMe drives have got completely different connector, so you cannot fit an NVMe drive into a SAS bay, and you can't fit a SAS or SATA drive into a NVMe bay.  

So that's all. Further we may cover on more. 

-DR