Messages in this thread |  | | Subject | Re: Linux and system area networks | From | Roland Dreier <> | Date | 25 Jun 2001 15:55:20 -0700 |
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>>>>> "Pete" == Pete Zaitcev <zaitcev@redhat.com> writes:
Roland> The rough idea is that WSD is a new user space library Roland> that looks at sockets calls and decides if they have to go Roland> through the usual kernel network stack, or if they can be Roland> handed off to a "SAN service provider" which bypasses the Roland> network stack and uses hardware reliable transport and Roland> possibly RDMA.
Pete> That can be done in Linux just as easily, using same DLLs Pete> (they are called .so for "shared object"). If you look at Pete> Ashok Raj's Infi presentation, you may discern "user-level Pete> sockets", if you look hard enough. I invite you to try, if Pete> errors of others did not teach you anything.
I think you misunderstood the point. Microsoft is providing this WSD DLL as a standard part of W2K now. This means that hardware vendors just have to write a SAN service provider, and all Winsock-using applications benefit transparently. No matter how good your TCP/IP implementation is, you still lose (especially in latency) compared to using reliable hardware transport. Oracle-with-VI and DAFS-vs-NFS benchmarks show this quite clearly.
Linux has nothing to compare to Winsock Direct. I agree, one could put an equivalent in glibc, or one could take advantage of Linux's relatively low system call latency and put something in the kernel. The unfortunate consequence of this is that SAN (system area network) hardware vendors are not going to support Linux very well.
BTW, do you have a pointer to Ashok Raj's presentation?
Roland> This means that all applications that use Winsock benefit Roland> from the advanced network hardware. Also, it means that Roland> Windows is much easier for hardware vendors to support Roland> than other OSes. For example, Alacritech's TCP/IP offload Roland> NIC only works under Windows. Microsoft is also including Roland> Infiniband support in Windows XP and Windows 2002.
Pete> IMHO, Alacritech is about to join scores and scores of Pete> vendors who tried that before. Customers understand very Pete> soon that a properly written host based stack works much Pete> better in the face of a changing environment: Faster CPUs, Pete> new CPUs (IA-64), new network protocols (ECN). Besides, it Pete> is easy to "accelerate" a bad network stack, but try to Pete> outdo a well done stack.
OK, how about an Infiniband network with a TCP/IP gateway at the edge? Have we thought about how Linux servers should use the gateway to talk to internet hosts? Surely there's no point in running TCP/IP inside the Infiniband network, so there needs to be some concept of "socket over Infiniband."
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