On 1/18/07, Jeff Anderson-Lee <[EMAIL PROTECTED]> wrote:
Rick McNeal wrote: > On Jan 18, 2007, at 12:00 PM, Mark A. Carlson wrote: > >> I would imagine the argument is that of software drivers >> for the storage stack consume much less overhead by >> cutting out the IP part - less CPU consumed, perhaps >> better throughput. As far as cost, it leverages the NIC >> commodity pricing curve without requiring TCP offload. > > The amount of CPU speed being consumed is really only valid for > underpowered machines. Any modern desktop has more then enough > horsepower to completely fill a 1GbE link with traffic at 4KB packet > sizes. I don't have OpenSolaris numbers at hand, but under Linux x86_64 on a server-class motherboard that doesn't seem to be the case. In a recent "echo"-style test, 4KiB UDP pegged one CPU of a dual 3.6GHz Xeon EM64T but only obtained 90MB/s for UDP and 63MB/s for TCP/IP (with no IPSEC). It didn't saturate the network until sending 16KiB packets for UDP and never did for TCP. Perhaps with a TCP offload engine under Solaris one might do better but... that's a lot of CPU power devoted just to flinging the bits.
I just tested a quick rcp, and got about 110MB/s between two twin UltraSparc machines, for the cost of about 2/3 of a 1.5GHz cpu. I know that pretty well anything over 1GHz can saturate a 1GbE link - I've seen well over 100MB/s serving NFS and doing backups and the machines are hardly breaking into a sweat. That's entry level hardware with no tweaking. Needless to say I have no idea how fast my Opteron boxes could go as I simply don't have the network capacity to test it (over 120MB/s and they're hardly even getting warmed up). -- -Peter Tribble http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/
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