On Fri, Jun 13, 2008 at 04:58:04PM -0700, Dean Hildebrand wrote: > The reason it is an art is that you don't know the hardware that exists > between the client and server. Talking about things like BDP is fine, > but in reality there are limited buffer sizes, flaky hardware, > fluctuations in traffic, etc etc. Using the BDP as a starting point > though seems like the best solution, but since the linux server doesn't > know anything about what the BDP is, it is tough to hard code any value > into the linux kernel. As you said, if we just give a reasonable > default value and then ensure people can play with the knobs. Most > people use NFS within a LAN, and to date there has been little if any > discussion on using NFS over the WAN (hence my interest), so I would > argue that the current values might not be all that bad with regards to > defaults (at least we know the behaviour isn't horrible for most people). > > Networks are messy. Anyone who wants to work in the WAN is going to > have to read about such things, no way around it. A simple google > search for 'tcp wan' or 'tcp wan linux' gives loads of suggestions on > how to configure your network, so it really isn't a burden on sysadmins > to do such a search and then use the given knobs to adjust the tcp > buffer size appropriately. My patch gives sysadmins the ability to do > the google search and then have some knobs to turn. > > Some sample tcp tuning guides that I like: > http://acs.lbl.gov/TCP-tuning/tcp-wan-perf.pdf > http://acs.lbl.gov/TCP-tuning/linux.html > http://gentoo-wiki.com/HOWTO_TCP_Tuning (especially relevant is the part > about the receive buffer) > http://www.linuxclustersinstitute.org/conferences/archive/2008/PDF/Hildebrand_98265.pdf > (our initial paper on pNFS tuning) Several of those refer to problems that can happen when the receive buffer size is set unusually high, but none of them give a really detailed description of the behavior in that case--do you know of any? --b. -- 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
