<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Yes I did some testing on the speed and it was much faster to write compressed, which did make sense to me since there was so much less data to write, and cpu time nothing next to i/o time.<div><br></div><div>I'll rerun the test again today.</div><div><br></div><div>C</div><div><br><div><div>On Nov 10, 2009, at 4:50 AM, Dean N. Williams wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">This is not what we experienced. In fact, I recall just the opposite. Charles Doutriaux did the work, so I'll let him respond directly. Also it would be good if Ed Hartnett and Russ Rew respond as well to the slowness that you are seeing. They may be able to help you on this.<div><br></div><div>Charles, if I recall correctly, were the zlib compressed netCDF files read faster in CDAT?<br><div><br></div><div>We are using CMOR2, in which CMOR2 does the DRS, netCDF-4 classic compressed output.</div><div><br></div><div>Best regards,</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Dean</div><div><br><div><div>On Nov 10, 2009, at 4:20 AM, <<a href="mailto:stephen.pascoe@stfc.ac.uk">stephen.pascoe@stfc.ac.uk</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"> <div> <div><font face="Arial" size="2"><span class="884391312-10112009">Hi Dean</span></font></div> <div><font face="Arial" size="2"><span class="884391312-10112009"></span></font> </div> <div><font face="Arial" size="2"><span class="884391312-10112009">In tests we've done at BADC we have experienced 10-20x slowdown in write speed with NetCDF4 compression. Is this typical and are modelling centres aware that they can expect a significant I/O bottleneck?</span></font></div> <div><font face="Arial" size="2"><span class="884391312-10112009"></span></font> </div> <div><font face="Arial" size="2"><span class="884391312-10112009">This makes me think, have we said CMIP5 data *must* be compressed? Is there a danger we will get a higher volume of data than we expect because it will be uncompressed to speed up the process at the modelling centres? How would we enforce NetCDF compression -- presumably it would be discovered during replication.</span></font></div> <div><font face="Arial" size="2"><span class="884391312-10112009"></span></font> </div> <div><font face="Arial" size="2"><span class="884391312-10112009">Cheers,</span></font></div> <div><font face="Arial" size="2"><span class="884391312-10112009">Stephen.</span></font></div> <div><font face="Arial" size="2"></font> </div> <div align="left"><font face="Arial" size="2">---</font></div> <div align="left"><font face="Arial" size="2">Stephen Pascoe +44 (0)1235 445980</font></div> <div align="left"><font face="Arial" size="2">British Atmospheric Data Centre</font></div> <div align="left"><font face="Arial" size="2">Rutherford Appleton Laboratory</font></div> <div> </div> <br><p>-- <br>Scanned by iCritical. </p> <br></div></blockquote></div><br></div></div></div></blockquote></div><br></div></body></html>