> -----Original Message----- > From: Trond Myklebust [mailto:Trond.Myklebust@xxxxxxxxxx] > Sent: Tuesday, January 18, 2011 6:57 PM > To: Muntz, Daniel > Cc: matt@xxxxxxxxxxxx; rees@xxxxxxxxx; > androsadamson@xxxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx; > bhalevy@xxxxxxxxxxx > Subject: RE: 4.1 no-pnfs mount option? > > On Tue, 2011-01-18 at 21:29 -0500, Daniel.Muntz@xxxxxxx wrote: > > > > > -----Original Message----- > > > From: Trond Myklebust [mailto:Trond.Myklebust@xxxxxxxxxx] > > > Sent: Tuesday, January 18, 2011 5:45 PM > > > To: Muntz, Daniel > > > Cc: matt@xxxxxxxxxxxx; rees@xxxxxxxxx; > > > androsadamson@xxxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx; > > > bhalevy@xxxxxxxxxxx > > > Subject: RE: 4.1 no-pnfs mount option? > > > > > > On Tue, 2011-01-18 at 19:53 -0500, Daniel.Muntz@xxxxxxx wrote: > > > > > > > > > -----Original Message----- > > > > > From: Trond Myklebust [mailto:Trond.Myklebust@xxxxxxxxxx] > > > > > Sent: Tuesday, January 18, 2011 11:15 AM > > > > > To: Matt W. Benjamin > > > > > Cc: Muntz, Daniel; rees@xxxxxxxxx; androsadamson@xxxxxxxxx; > > > > > linux-nfs@xxxxxxxxxxxxxxx; Benny Halevy > > > > > Subject: Re: 4.1 no-pnfs mount option? > > > > > > > > > > On Tue, 2011-01-18 at 13:46 -0500, Matt W. Benjamin wrote: > > > > > > Hi, > > > > > > > > > > > > Isn't by mount a plausible way to select for pnfs > > > > > independent of debugging? Is it assured that a client > > > > > administrator would never reasonably wish to do this? > > > > > > > > > > "Why would an administrator never want to do this?" is > > > not a helpful > > > > > question. > > > > > > > > > > A more useful question is "what reason would you > possibly have for > > > > > overriding the server's request that you do pNFS when > > > your client has > > > > > pNFS support?" What makes pNFS so special that we must allow > > > > > administrators to do this on a per-mount basis? > > > > > > > > By the same logic, why should a user be allowed to select > > > which version of NFS they use for mounting when the server > > > has a perfectly reasonable way of negotiating it? Getting to > > > choose v2 vs. v3 vs. v4 seems like much less of a distinction > > > than choosing between pNFS and no pNFS. Frankly, it never > > > even occurred to me that there wouldn't be a mount option to > > > make this choice. Enabling/disabling the layout driver > > > doesn't fit the existing model of choosing mount behavior, > > > and is a big hammer--it's all or nothing. > > > > > > > > Anyway, here's a use case: I'm working at an > > > HPC/gas+oil/satellite data site. We have an awesome pNFS > > > server for our big data and I want to access my big data with > > > pNFS. We have another server for homedirs, some big data, > > > and other stuff. Some mounts are fine with pNFS, others are > > > abysmal. So, I want to mount some directories with pNFS, and > > > some without pNFS, on the same client, independent of the > > > server configuration. > > > > > > mount -t nfs -overs=4,minorversion=0 foo:/ /bar > > > > > > Done... Any more questions? > > > > Several, but I'll stick to one rhetorical. Does NFSv4.1 > have any features, other than pNFS, that are not in 4.0? > > Why stop now, when you were batting 100? I told you what the criteria > were for adding more mount options, and you start whining about not > being able to conceive of a world without mount options. > > The point is that NFSv4.1 was supposed to let the _server_ tell the > client when to use pNFS. The reason why you let the _server_ > do this, is > because pNFS is about enabling _server_ scalability. It is not about > faster clients... > If you don't want the client to use pNFS, then fix the _server_ > settings... I don't miss the kiss-up-kick-down model of software development... The criteria was a use case, so I gave a use case. I wouldn't rule out the "testing use case" either, as a mount option makes it possible to test mixed pnfs/non-pnfs 4.1 traffic without multiple servers. The point is that pNFS, like everything else, is about the users. -Dan > > -- > Trond Myklebust > Linux NFS client maintainer > > NetApp > Trond.Myklebust@xxxxxxxxxx > www.netapp.com > > > -- 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
