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> Faster file sharing: Windows 10 Pro for Workstations includes a feature called SMB Direct, which supports the use of network adapters that have Remote Direct

> Faster file sharing: Windows 10 Pro for Workstations includes a feature called SMB Direct, which supports the use of network adapters that have Remote Direct Memory Access (RDMA) capability. Network adapters that have RDMA can function at full speed with very low latency, while using very little CPU. Interesting to see file copy speeds mentioned. "Drag-and-drop" file copy has a known bottleneck that other methods (robocopy, copy-item, etc) do not have, and I wonder if this improvement will improve all copy methods, or just "Drag-and-drop". Also interested in the security considerations for having DMA (Direct memory access) to a remote PC for SMB. Presumably this would be for authenticated users/sessions. Yet SMB has been a recently-leveraged protocol for ransomware attacks.

youdontknowtho 9y ago
SMB 3 hasn't been part of the ransomeware attacks. It was SMB 1. SMB 3 can use RDMA and is insanely fast. I'm not sure how SMB over RDMA is supposed to work on a workstation, though. It's only been used for file servers and clusters at this point.
- deleted 9y ago
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cjsuk 9y ago
It won't make a damn bit of difference for a lot of users. Most of the horrible performance I find for windows file copies (and git/svn checkouts etc) is due to MFT contention in the filesystem rather than the network layer. This is for the "average user" scenario rather than fileserver however. This apparently hasn't gone away with ReFS either but I haven't personally tested it.
rbanffy 9y ago
Why would a filesystem have to know about a network interface's ability do do RDMA? Shouldn't the kernel use it when it makes sense and leave the filesystem to be concerned with files? RDMA can speed up a lot of things besides remote file access.
- stephengillie 9y ago
  The goal here appears to be avoiding involving the main CPU, letting the network adapter write directly to arbitrary memory. Currently, DMA allows network adapters to write to a ring buffer in memory, and the free space remaining is transmitted in TCP packets as the window size. This ring buffer is limited in size, requiring the CPU to copy data to other memory locations. Will RDMA be giving network adapters the ability to write directly to any memory location, instead of just the ring buffer? Does it include memory-mapped devices - does this technology let you remotely access the memory space mapped to a USB webcam?

youdontknowtho 9y ago

SMB 3 hasn't been part of the ransomeware attacks. It was SMB 1. SMB 3 can use RDMA and is insanely fast. I'm not sure how SMB over RDMA is supposed to work on a workstation, though. It's only been used for file servers and clusters at this point.

deleted 9y ago
[deleted]

cjsuk 9y ago

It won't make a damn bit of difference for a lot of users. Most of the horrible performance I find for windows file copies (and git/svn checkouts etc) is due to MFT contention in the filesystem rather than the network layer. This is for the "average user" scenario rather than fileserver however. This apparently hasn't gone away with ReFS either but I haven't personally tested it.

rbanffy 9y ago

Why would a filesystem have to know about a network interface's ability do do RDMA? Shouldn't the kernel use it when it makes sense and leave the filesystem to be concerned with files? RDMA can speed up a lot of things besides remote file access.

stephengillie 9y ago
The goal here appears to be avoiding involving the main CPU, letting the network adapter write directly to arbitrary memory. Currently, DMA allows network adapters to write to a ring buffer in memory, and the free space remaining is transmitted in TCP packets as the window size. This ring buffer is limited in size, requiring the CPU to copy data to other memory locations. Will RDMA be giving network adapters the ability to write directly to any memory location, instead of just the ring buffer? Does it include memory-mapped devices - does this technology let you remotely access the memory space mapped to a USB webcam?