Notify me of new comments via email. Notify me of new posts via email. August 28, August 28, Abhinav Mahapatra. This causes a lot of unused bandwidth which is the primary issue with TCP being really lossy protocol Now, coming to the lossless aspect of things. Share this: Twitter Facebook.
Like this: Like Loading Leave a Reply Cancel reply Enter your comment here Fill in your details below or click an icon to log in:. Email required Address never made public. Name required. When a fault occurs, link failover takes a long time, thus interrupting storage services.
Service changes can be automatically synchronized to the entire network after being configured at a single point, greatly improving the service provisioning efficiency. The solution takes full advantage of the million-level IOPS of all-flash storage and meets the petabyte-level development requirements of the financial industry.
Looking forward, Huawei will continue to adhere to its customer-centric business strategy and work with partners to develop new and improve existing storage network practices.
This will likely see Huawei surge to the forefront of all innovation across different industry scenarios, and make Huawei the first stop in enterprise digital transformation. All rights reserved. Reminder To have a better experience, please upgrade your IE browser. Login User Name. Forgot password? Change password No account? Create one! Many readers may correctly complain of having heard this debate repeatedly, with some of the players switching sides over the course of the years, and they are right!
When the speed of Ethernet was low e. Today, with 10GE available and 40GE and GE in our close future, the serialization delay is low enough to justify looking at this topic again. Today many Ethernet switches are designed with a store-and-forward architecture, since this is a simpler design. Store-and-forward adds several serialization delays inside the switch and therefore the overall latency is negatively impacted [10].
Cut-through switches have a lower latency at the cost of a more complex design, required to save the intermediate store-and-forward. This is possible to achieve on fixed configuration switches like the Nexus , but much more problematic on modular switches with a high port count like the Nexus In modular switches, backplane switching fabrics are multiple also to improve high availability, modularity, and serviceability and run dedicated links toward the linecards at a speed as high as possible.
Modular switches may have thousands of ports because they may have a high number of linecards and a high number of ports per linecard. Therefore, a store and forward between the ingress linecard and the fabric and a second one between the fabric and the egress linecard are almost impossible to avoid.
Cut-through switching is not possible if there are frames already queued for a given destination and if the speed of the egress link is higher than the speed of the ingress link data underrun. Finally, cut-through switches cannot discard corrupted frames, since when they detect that a frame is currupted, by examining the Frame Control Sequence FCS , they have already started transmitting that frame.
The latency parameter that cluster users care about is the latency incurred in transferring a buffer from the user memory space of one computer to the user memory space of another computer.
The main factors that contribute to the latency are. The term native support for storage traffic indicates the capability of a network to act as a transport for the SCSI protocol.
Figure illustrates possible alternative SCSI transports. SCSI was designed assuming the underlying physical layer was a short parallel cable, internal to the computer, and therefore extremely reliable. Based on this assumption, SCSI is not efficient in recovering from transmission errors.
A frame loss may cause SCSI to time-out and recover in up to one minute. For this reason, when the need arose to move the storage out of the servers in the storage arrays, the Fibre Channel protocol was chosen as a transport for SCSI.
A proper implementation of the PAUSE mechanism achieves results identical to a credit-based flow control scheme, in a distance-limited environment like the Data Center. In the latter case the buffer resides in the user memory rather than in the kernel of a process. The buffer must be transferred to the user memory of another process.
User memory is virtual memory, and it is therefore scattered in physical memory. The RDMA operation must happen without CPU intervention, and therefore the NIC must be able to accept a command to transfer a user buffer, gather it from physical memory, implement a reliable transport protocol, and transfer it to the other NIC. The receiving NIC must verify the integrity of the data, signal the successful transfer or the presence of errors, and scatter the data in the destination host physical memory without CPU intervention.
In the IP world, there is no assumption on the reliability of the underlying network. Packets dropped by the underlying network are recovered by TCP through retransmission. Over networks with limited scope, such as Data Center networks, in-order frame delivery can be achieved without using a heavy protocol such as TCP. As an example, in-order frame delivery is successfully achieved by Fibre Channel fabrics and Ethernet networks.
As discussed in Chapter 2, Ethernet can be extended to become lossless. In Lossless Ethernet dropping happens only because of catastrophic events, like transmission errors or topology reconfigurations. The RDMA protocol may therefore be designed with the assumption that frames are normally delivered in order without any frame being lost. I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands.
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