Messages in this thread |  | | Subject | Re: "raw" block devices? | Date | Fri, 18 Oct 96 17:26:09 PDT | From | Craig Milo Rogers <> |
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>On Thu, 17 Oct 1996, Theodore Y. Ts'o wrote: > >> [...] One of the ways how the SGI gets truely >> awesome web server benchmarks is by doing zero-copy disk reads from the >> filesystem, and zero-copy network writes. All you need the CPU for is >> to set up the DMA's, lock down the memory pages, and stay out of the >> way. :-) > >... and you need a network card that does hardware checksumming :(((
However, if you use a typical Ethernet LAN, then your network card already does hardware checksumming. Of course, this is Ethernet frame-level checksumming, not, IP- or TCP-level checksumming, but there may be circumstances in which you can trust the LAN and locally-connected hosts sufficiently to defer or avoid the IP- or TCP-level checksums. (As an analogy, you sorta squint sideways at your LAN-connected workstations and fileservers, and declare them all components of a single computer system with the LAN as its internal memory bus.)
Another option is to give each individual disk drive its own IPv6 address, and have it transmit directly to the network, bypassing the "system" CPU.
The Netstation project at ISI has researched some of these issues; please see:
http://www.isi.edu/div7/netstation/
Craig Milo Rogers
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