[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[netCDFJava #BNA-191717]: chunking in Java

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: [netCDFJava #BNA-191717]: chunking in Java
  • Date: Fri, 02 May 2014 13:28:14 -0600
Hi Jeff,

How chunking and compression affect file size and read/write performance is a 
complex issue. I'm going to pass this along to our chunking expert (Russ Rew) 
who, I believe, is back in the office on Monday and should be able to provide 
you with some better advise than I can give.

In the mean time, here's an email he wrote in response to a conversation on the 
effect of chunking on performance that might be useful:

http://www.unidata.ucar.edu/mailing_lists/archives/netcdfgroup/2013/msg00498.html

Sorry I don't have a better answer for you.

Ethan 

Jeff Johnson wrote:
> Ethan-
> 
> I made the changes you suggested with the following result:
> 
> 10000 records, 8 bytes / record = 80000 bytes raw data
> 
> original program (NetCDF4, no chunking): 537880 bytes (6.7x)
> file size with chunk size of 2000 = 457852 bytes (5.7x)
> 
> So a little better, but still not good. I then tried different chunk sizes
> of 10000, 5000, 200, and even 1, which I would've thought would give me the
> original size, but all gave the same resulting file size of 457852.
> 
> Finally, I tried writing more records to see if it's just a symptom of a
> small data set. With 1M records:
> 
> 8MB raw data, chunk size = 2000
> 45.4MB file (5.7x)
> 
> This is starting to seem like a lost cause given our small data records.
> I'm wondering if you have information I could use to go back to the archive
> group and try to convince them to use NetCDF3 instead.
> 
> jeff


Ticket Details
===================
Ticket ID: BNA-191717
Department: Support netCDF
Priority: Normal
Status: Open