On 06/07/2010 09:49 PM, J. Bruce Fields wrote: >> >> It's a know problem with a network storage cluster. What happens is >> that with 8of8 all the clients exercise all of the nodes at the same >> time so they are clashing on the network. > > OK, so if two clients are both trying to send a stripe of data to the > same OSD data at the same time, absent a switch that could somehow > afford to queue up a full stripe-unit's worth of data, packets get lost? > It's tcp they don't get lost, per-se they just get queued up. And that tcp ramp up and all that, you know. We use a 64k stripe unit with say raid of 4-8 that's 256k-1M bytes in a stripe. I don't think a network buffer that big will help at all. It'll just delay everything more. The best is a sound statistical network strategy that'll let the system even out overall. (Or not ...) > (Also, out of curiosity: do you know of any papers or documentation that > describe that problem in more detail?) > Personally, I'm privileged to learn from the best here at Panasas. CC: Brent, Can you recommend to Bruce some good papers about raid groups and network SAN strategies? > --b. Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
