Hi Kirk,
On Mar 25, 2010, at 4:03 PM, [email protected] wrote:
> Mark,
>
> I am new to HDF5 and still working my way through the Tutorials. It looks
> promising thus far, but have been concerned about the Circular Database
> implementation.
> The dataset size will be static based upon the time duration for which I
> want to provide data lookup and the data output rate of the sensors. I
> suppose what I need to figure out then, based on your approach, is how to
> "seek" to the appropriate location (record) within the dataset for
> continued writing of the data. This is probably where your suggestion of
> adding an attribute (time of acquisition) comes into play.
You probably want to use a hyperslab or point selection for writing to
your dataset in the file. (H5Sselect_hyperslab() or H5Sselect_elemets())
Quincey
> Thanks for the reassurance and the tips,
> Kirk
>
>> You should be able to do that pretty easily with HDF5.
>>
>> If you are absolutely certain your datasets will never, ever change in
>> size, you could create an 'empty' database by going through and creating
>> N datasets (H5Dcreate) of desired size (H5Screate_simple) but not
>> actually writing anything to any of the datasets.
>>
>> Then, as time evolves, you pick a particular dataset to open (H5Dopen),
>> write to (writing afresh if the dataset has yet to be written to or
>> overwriting whats already there if it has already been written to --
>> makes no difference to the application. It just calls H5Dwrite) and
>> H5Dclose.
>>
>> If you think you might want to be able to vary dataset size over time,
>> use 'chunked' datasets (H5Pset_chunk) instead of the default
>> (contiguous). If you need to maintain other tidbits of information about
>> the datasets such as time of acquisition, sensor # (whatever), and that
>> data is 'small' (<16kb), attach attributes (H5Acreate) to your datasets
>> and overwrite those attributes as you would datasets (H5Aopen, H5Awrite,
>> H5Aclose).
>>
>> Mark
>>
>>
>> On Thu, 2010-03-25 at 13:11, [email protected] wrote:
>>> I am interested in using HDF5 to manage sensor data within a continuous
>>> Circular Database/File. I wish to define a database of a fixed size to
>>> manage a finite amount of historical data. When the database file is
>>> full
>>> (i.e. reach the defined capacity) I would like to begin overwriting the
>>> oldest data within the file.) This is for an application for a system
>>> where I only care about the most recent data over a specific duration
>>> with
>>> obvious constraints on the amount of storage available.
>>>
>>> Does HDF5 have such capability or is there a recommended
>>> approach/suggestions anyone has?
>>>
>>> Best Regards,
>>> Kirk Harrison
>>>
>>>
>>>
>>> _______________________________________________
>>> Hdf-forum is for HDF software users discussion.
>>> [email protected]
>>> http://*mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
>> --
>> Mark C. Miller, Lawrence Livermore National Laboratory
>> ================!!LLNL BUSINESS ONLY!!================
>> [email protected] urgent: [email protected]
>> T:8-6 (925)-423-5901 M/W/Th:7-12,2-7 (530)-753-851
>>
>>
>> _______________________________________________
>> Hdf-forum is for HDF software users discussion.
>> [email protected]
>> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
>>
>
>
>
> _______________________________________________
> Hdf-forum is for HDF software users discussion.
> [email protected]
> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
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