Return-Path: Received: from mail-wm0-f49.google.com ([74.125.82.49]:38769 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946693AbcBROiU convert rfc822-to-8bit (ORCPT ); Thu, 18 Feb 2016 09:38:20 -0500 Received: by mail-wm0-f49.google.com with SMTP id a4so28351519wme.1 for ; Thu, 18 Feb 2016 06:38:20 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20160218141447.GB4256@fieldses.org> References: <20160217205929.GF10401@fieldses.org> <3B48A59F-638A-45C9-B2E4-2D65C00DE639@netapp.com> <20160218141447.GB4256@fieldses.org> From: Martin Houry Date: Thu, 18 Feb 2016 15:38:00 +0100 Message-ID: Subject: Re: "Re: [PATCH RFC Version 1 0/6] Request for Comment: NFS4.1 Session Trunking" To: "J. Bruce Fields" Cc: Trond Myklebust , Chuck Lever , "Adamson, Andy" , Linux NFS Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: Can we let the choice to the client if the session trunking is manual or automatic? Manual : with the load-balancing algorithm of his choice Automatic : with a smarter algorithm just as M. Fields says, like an adaptative load-balancing algo. for example. Martin 2016-02-18 15:14 GMT+01:00 J. Bruce Fields : > On Wed, Feb 17, 2016 at 06:55:43PM -0500, Trond Myklebust wrote: >> On Wed, Feb 17, 2016 at 5:52 PM, Chuck Lever wrote: >> > >> >> On Feb 17, 2016, at 5:35 PM, Adamson, Andy wrote: >> >> The fs_locations would need to be requested by the client. I guess we reqest them at every mountâ€Ķ. >> > >> > Yep, and fetch them again every so often. There's no real >> > cache coherency protocol for this information. (That's >> > where a pNFS layout might be more valuable). >> >> If your goal is to do session trunking, you only really need to check >> the fs_locations attribute on the root file system. (so >> GETROOTFH+GETATTR(fs_locations)). That's the natural place for a >> server to advertise its full set of IP addresses, and the session >> trunking protocol itself will allow you to winnow out any that might >> belong to a replica server. > > I worry that round-robin could behave really badly if the client's path > to the two IP addresses have different performance characteristics. But > a server should probably still be allowed to advertise those as replicas > (e.g. maybe a slower interface is usable as a fallback?). > > So maybe we should be careful about making this automatic. Unless the > load-balancing is a little smarter than pure round robin. Or unless we > can get some more fine-grained information (maybe someone could use > fs_location_info's preference information for this?). > > --b. > >> >> You might want to refresh that info whenever the connection goes away >> on one or more addresses without a reboot so you can detect when NICs >> are going away. >> >> Otherwise, polling every couple of hours or so for new NICs shouldn't >> be too burdensome... >> >> Cheers, >> Trond