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>To: address@hidden >From: Éaddress@hidden >Subject: Re: 20030919: NetCDF/HDF5 Proposal Approved >Organization: CNRC >Keywords: 200309191351.h8JDpWk1005725 Hi Éric, > Do you know if the proposed netCDF-4 will still support the netCDFv2 > interface? And with the HDF5 lower layer, is random-access (direct > disk-access) still going to work? Yes, it is our intention to support the netCDF version 2 interfaces, since these are just a layer on top of netCDF-3, which will be supported. Direct access is still available in HDF5, and it may take either more or fewer seeks to access the same data as with netCDF, depending on how your the data is written. As an example, when you declare an unlimited dimension, the data is "chunked" or tiled, which may mean fewer disk accesses to get various cross sections of data than with the netCDF format. So we already know that using HDF5 may result in slower or faster I/O performance than netCDF, depending on circumstances. What we don't know yet is how close we can get to current netCDF performance. By the way, we also intend to try to support read and write access to netCDF format data as well as netCDF-4 written HDF5 data through the netCDF-4 interface. And we are currently implementing a netCDF-3 interface on HDF5 which will include netCDFv2 interfaces, as a proof of concept for our backward-compatibility approach ... --Russ