Re: [nfsv4] Barry Leiba's No Objection on draft-ietf-nfsv4-minorversion2-40: (with COMMENT)
Tom Haynes <thomas.haynes@primarydata.com> Mon, 25 January 2016 20:00 UTC
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From: Tom Haynes <thomas.haynes@primarydata.com>
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Date: Mon, 25 Jan 2016 11:59:54 -0800
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To: Barry Leiba <barryleiba@computer.org>
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Cc: nfsv4-chairs@ietf.org, The IESG <iesg@ietf.org>, nfsv4@ietf.org, draft-ietf-nfsv4-minorversion2@ietf.org
Subject: Re: [nfsv4] Barry Leiba's No Objection on draft-ietf-nfsv4-minorversion2-40: (with COMMENT)
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Hi Barry, Thanks for the comments! Responses inline: > On Jan 20, 2016, at 3:53 PM, Barry Leiba <barryleiba@computer.org> wrote: > > Barry Leiba has entered the following ballot position for > draft-ietf-nfsv4-minorversion2-40: No Objection > > When responding, please keep the subject line intact and reply to all > email addresses included in the To and CC lines. (Feel free to cut this > introductory paragraph, however.) > > > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > for more information about IESG DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-nfsv4-minorversion2/ > > > > ---------------------------------------------------------------------- > COMMENT: > ---------------------------------------------------------------------- > > I appear to be in the minority here, in that I *did* understand this > document's place relative to 4.0, and 4.1. Still, I agree that > clarifying that is really important, and I'll suggest a specific > clarification in Section 1.1): > > OLD > This document describes the NFSv4.2 protocol. With respect to > NFSv4.0 and NFSv4.1, this document does not: > NEW > This document describes the NFSv4.2 protocol as extensions to > the specifications of NFSv4.0 and NFSv4.1. Those specifications > remain current and form the basis for the additions defined > herein. It is necessary to implement those before adding > NFSv4.2 to the implementation. > > With respect to NFSv4.0 and NFSv4.1, this document does not: > END As noted in the reply to Dave Noveck, I took his counter-proposal. > > -- Section 1.2 -- > > A major goal of the design of NFSv4.2 is to take common local file > system features and offer them remotely. > > This sounds like it means to be a change in goals relative to 4.0 and > 4.1. I think it would fit better to say it this way, and would add to > the clarification above: > > NEW > A major goal of the enhancements provided in NFSv4.2 is to take > common local file system features that have not been available > through earlier versions of NFS, and to offer them remotely. > END I’m fine with that change. > > -- Section 6.1 -- > > Hole: A byte range within a Sparse file that contains regions of all > zeroes. A hole might or might not have space allocated or > reserved to it. > > I'm wondering about the "regions of" here: If I have a byte range that > contains two regions of all zeroes and something that's not all zeroes in > between those two regions, I do not have a (single) hole, do I? No, you have two. > Why does > this say "regions of”? When I read it as you’ve laid it out, I agree with you. I thought of taking off the plural, but I like this better: Hole: A byte range within a Sparse file that contains all zeroes. A hole might or might not have space allocated or reserved to it. > > And a question: Is there any disctinction between a byte-range within a > sparse file that happens to contain all zeroes... and one that is > recorded in metadata as being all zeroes? As far as the local filesystem, yes. As far as transferring across the wire, no. > Can some file systems write a > region of zeroes without "knowing" that they have created a hole? Does > this distinction matter here? The way it matters is that we know we do not have to transfer the data across the wire. > > -- Section 6.2.1 -- > > Note that as the client has no a priori > knowledge of whether a hole is present or not > > (No need to respond to this; take it or leave it as you please.) I have > a general preference for avoiding Latin terms, as they're not properly > understood by everyone. In this case, too, "a priori" has a connotation > that goes beyond the literal Latin translation. I think it'd be better > to word this as "Because the client does not know in advance whether a > hole is present or not”. I’m fine with not appearing so stiff. :-) Taken. > > READ_PLUS extends the response with a new arm representing holes to > avoid returning data for portions of the file which are initialized > to zero and may or may not contain a backing store. Returning data > blocks of uninitialized data wastes computational and network > resources, thus reducing performance. > > It wouldn't be "uninitialized" data, would it? It'd be zeroes. I think > you might just want to say "Returning actual data blocks corresponding to > holes", yes? Yes > > By contrast, if a READ_PLUS occurs in the middle of a hole, > the server can send back a range which starts before the offset and > extends past the range. > > I'm not sure how a range can extend past itself ("a range which ... > extends past the range"). I think you just want to say "a range > representing the hole.” How about this? By contrast, if a READ_PLUS occurs in the middle of a hole, the server can send back a range which starts before the offset and extends past the requested length. > > -- Section 6.2.2 -- > > DEALLOCATE can be used to hole punch, which allows the client to > avoid the transfer of a repetitive pattern of zeros across the > network. > > This is the first time you've mentioned DEALLOCATE where I think I > understand that it is a way of doing a WRITE wherein the client sends the > representation of a hole to the server, rather than actually doing a > WRITE. (I had previously thought it was used to tell the server to undo > an ALLOCATE, but it now seems that they are related things, but are not > duals.) > > You might want to be more clear about this here, especially if what I say > in the previous paragraph is wrong. No, it is another form of WRITE and it is why we did not provide WRITE_PLUS. Does this work better for you? The client can use the DEALLOCATE operation on a range of a file as a hole punch, which allows the client to avoid the transfer of a repetitive pattern of zeros across the network. This hole punch is a result of the unreserved space returning all zeros until overwritten. > > -- Section 7 -- > > Lesser space MAY be > consumed for backups after block deallocation. > > I don't think this is a proper 2119 MAY; it sounds like a statement of > fact, not a protocol option. > > Agreed.
- [nfsv4] Barry Leiba's No Objection on draft-ietf-… Barry Leiba
- Re: [nfsv4] Barry Leiba's No Objection on draft-i… David Noveck
- Re: [nfsv4] Barry Leiba's No Objection on draft-i… Barry Leiba
- Re: [nfsv4] Barry Leiba's No Objection on draft-i… Tom Haynes
- Re: [nfsv4] Barry Leiba's No Objection on draft-i… Tom Haynes
- Re: [nfsv4] Barry Leiba's No Objection on draft-i… Barry Leiba