[AFS3-std] Re: AFS-3 64-bit time I-D

[Jeffrey Altman]

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On 3/11/2011 12:54 PM, Andrew Deason wrote:
> On Fri, 11 Mar 2011 12:30:05 -0500
> Jeffrey Altman <jaltman@secure-endpoints.com> wrote:
>=20
>> My point is that it is impossible to know the granularity in this
>> case.  Transmitting additional granularity information doesn't help
>> when it is unknown.
>=20
> True. In such cases the only thing that I see that can be done is that
> you flatten everything to some guessed resolution and say "it works up
> to 1ms; good enough". But right now in the existing draft, this
> determination is made by whomever generates the timestamp, which
> definitely does not seem correct.
>=20
> What about a representation for "unknown resolution"? Just, say,
> 0xffffffff in the resolution field (or perhaps 0x00000000) means "I
> don't know the resolution". We could cap that to mean "at most 1s
> resolution", since I don't think anything less granular than that is to=
o
> common or reasonable (and we do 1s granularity right now anyway, so...)=


Every NTFS file timestamp on Windows is 100ns resolution.
ZFS has micro-second resolution.

These discussions have to be held outside of the context of the OpenAFS
implementation.  I realize that is the only implementation that you work
on but its not the only implementation of these protocols.

OpenAFS is going to have to modify its on-disk data structures to make
use of 100ns resolution.  It needs to do that anyway because the
existing on-disk representation can't handle 64-bit values correctly in
any case.

However, that is independent of this document and the wire protocol.  A
decision to treat all values as having 1s granularity is an
implementation decision based upon its capabilities.

Jeffrey Altman



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