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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
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Dennis et al, Now on a more positive note, my early testing finds that an older utility program reads those new superblock 0 files just fine. So far, I checked only the three ref_hdf5_compat files from the new distro, and one test file that I created locally. This demonstrates the backward compatibility that we have been seeking. --Dave On Fri, Jun 3, 2016 at 5:26 PM, Dave Allured - NOAA Affiliate < dave.allured@xxxxxxxx> wrote: > Dennis, > > I use a simple hex dump for expediency. This misses files with a nonzero > user block, but I think those are pretty rare in the climate community. > > For example, here is one of the test files in the latest Unidata distro. > But I get the same result with a locally created file. > > mac56:~/netcdf/netcdf-c-4.4.1-rc2/nc_test4 55> od -tx1 -N9 > ref_hdf5_compat2.nc > 0000000 89 48 44 46 0d 0a 1a 0a 00 > 0000011 > > The superblock version number is the 9th (last) byte. > > This number matches what is reported by ncdump -hs in the new release. I > have no reason to doubt the result from H5Pget_version. > > --Dave > > > On Fri, Jun 3, 2016 at 4:59 PM, dmh@xxxxxxxx <dmh@xxxxxxxx> wrote: > >> HDF says the (superblock format) differences are: >> Version 0 is the default format >> Version 1 is the same as version 0 but with the “Indexed Storage >> Internal Node K” field for storing non-default B-tree ‘K’ value. >> Version 2 has some fields eliminated and compressed from superblock >> format versions 0 and 1. It has added checksum support and >> superblock extension to store additional superblock metadata. >> Version 3 is the same as version 2 except that the field “File >> Consistency Flags” is used for file locking. This format version >> will enable support for the latest version. >> It is possible that the H5Pget_version indicates not the true number, >> but rather the lowest externally detectable version number or some such. >> Do you have a pure hdf5 1.10 file to see that superblock number is >> reported by ncdump -hs? >> Or did you do a hex dump to see what is actually in the superblock? >> =Dennis Heimbigner >> Unidata >> >> >> On 6/3/2016 4:11 PM, Dave Allured - NOAA Affiliate wrote: >> >>> Netcdf group, >>> >>> My team is starting to test netcdf-4.4.1-rc2 with the latest HDF5 >>> library, currently 1.10.0-patch1. I see that netcdf-4 files are now >>> being generated with superblock version 0 for the first time in the >>> history of netcdf-4. Presumably this is a result of the recent format >>> compatibility fix in 4.4.1. >>> >>> All the older netcdf-4 files that I sampled, back to the original >>> netcdf-4.0 (2008), were created as superblock version 2. >>> >>> Are there any indications whether superblock 0 will be robust and >>> interoperable, going into the future? >>> >>> --Dave >> >>
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