Path: utzoo!attcan!uunet!mailrus!uflorida!novavax!hcx1!cliff From: cliff@SSD.CSD.HARRIS.COM (Cliff Van Dyke) Newsgroups: comp.protocols.nfs Subject: Re: Mountd loops in case of multiple mount requests. Message-ID: <4290@hcx1.SSD.CSD.HARRIS.COM> Date: 25 May 90 14:18:40 GMT References: <2143@inews.intel.com> Sender: news@hcx1.SSD.CSD.HARRIS.COM Organization: Harris Computer Systems, Fort Lauderdale, FL Lines: 35 In article <2143@inews.intel.com> kgarimel@hobbes.intel.com (Krishna Garimella) writes: >On a file server, the mountd becomes inoperative in certain cases, >when it is hit with many simultaneous mount requests from NFS clients. >We have different flavours of clients(Suns, GPXs, 3100s, SISOs ...). >This situation arises from a mass reboot of the clients(eg Power >glitch/faliure) > >Even when the mountd is killed and restarted, it "caters" to one (or two) >mount requests and then goes into a loop. The clients give timeout >messages. I've seen a substantially similar problem (but with ypserv) which I traced down to an unfortunate implementation of the UDP version of RPC. (This was a straight port of Sun's version 3.2 reference port.) The problem occurred when oodles of processes simultaneously accessed ypserv. ypserv would respond to the requests in FIFO order. Meanwhile, the clients got tired of waiting, timed out, and requested again. The server was so busy handling requests that had already timed out that it didn't have a chance to handle the new requests. The problem is significantly alleviated in Sun's 4.0 version of the reference port. Each retry done by the client is backed off by a factor of 2 reducing the load on the server. Do you know which rev is being used by your various clients? In general the algorithms used for the UDP version of RPC in the applications (e.g., ypserv and mounted) and the kernel (e.g., NFS and lockd) leave much to be desired. I suspect some mechanism which uses the history of previous performance of a server would prove to be most beneficial. -- Cliff Van Dyke cliff@ssd.csd.harris.com Harris Computer Systems ...!{uunet,novavax}!hcx1!cliff 2101 W. Cypress Creek Rd. Ft. Lauderdale, FL 33309-1892 Tel: (305) 973-5349