On 29 March 2011 11:32, Anthony <akcentos at anroet.com> wrote: > On 29/03/11 11:29, mcclnx mcc wrote: >> To answer your questios: >> >> 1. network is Intranet not internet. >> >> 2. servers CPU and I/O are very light. We did use "sar -u" and sar -b to check. >> >> 3. is NOT only one server has this network slow problem. at least 4 to 5 servers on that rack all report slow. it is NOT possible all servers on that rack are all heavy load. >> Expanding on Tym's reply i would also check the counters on the switch interfaces that serve that rack to look for packet drops or buffer problems at the time of the slowdown. Also look for the cpu utilisation on the switch in question in case it is being overwhelmed with control plane traffic That would seem to be the most likely explanation for 4 or 5 servers going slow at the same time. mike