Scribed by Haruki Oh
The Role of FCoE in I/O Consolidation
Summary:
This paper explores the possibility and benefit of Fibre Channel over Ethernet protocol to consolidate multiple traffic types in datacenters. The greatest benefit of consolidating multiple traffic type is the significant reduction in the number of wires and switches, and power consumption.
Internal SCSI is a popular transport protocol but it relies on TCP to recover from lost frames and complex gateways for managing states. Lossless network will provide a significant performance increase for iSCSI.
In order to put fibre channel over ethernet, we need ethernet to support jumbo frames to encapsulate fibre channel frames. To implement lossless network, full duplex links are used so that a receiver can pace the reception by requesting the sender to pause.
Opinion:
This paper had a comprehensive description of FCoE: what it is, how it can be used, and what the current state of the technology is. This is one of the few papers we read where the topic of the paper was practical for mass implementation.
UNH_IOL Fibre Channel Tutorial
Summary:
This tutorial gives an overview of fibre channel. Fibre channel offers advantages in price, reliability, performance, and practicality over network and channels. In particular, SCSI can use fibre channel for faster speed and scalability.
Fibre channel is divided into FC-0 through FC-4 layers. FC-0 being the physical implementation of the connection, FC-2 provides the transport, FC-3 gives advanced features, and FC-4 is the interface to applications, such as SCSI and IP.
Fibre channel has three topologies: point-to-point, arbitrated loop, and fabric, which is the most commonly used. Fabric topology is a cross-point switched configuration where multiple devices can communicate at the same time. Buffer-to buffer flow control is implemented with a credit based system, where sender can transmit the amount the credit allows. QoS is also supported.
Opinion:
I think this tutorial went straight into the description of lower level details without going through a detailed higher level description of what fibre channel is. It was a bit unclear how FC is better than Channel and network.
Discussion:
-Storage is a multi-billion dollar industry but received little attention from academia
-Storage product generally consists of many physical harddrives, and virtual drives run on top of them.
-Lossless communication is important because disk can crash if packets were lost
-Lossless is really lossless: Tom shared a story of a hardware bug where the hardware drops one packet a month, and the nightmare of debugging effort.
-Buffer to buffer credit system can control the flow and prevent buffer overflow.
-GOODS: simple, low overhead, lossless, multi-pathing
-BADS: can’t go long distance, weak interoperability, complicated, not economically scale, no congestion handling, not routable (layer-2 only), and monopolized industry
