Thanks Stephen and Jonathan for pointing this important things out. Now I begin to understand the importance of mmimportfs/mmexportfs for operations like the one I discuss here. Will let you know how it goes.
2018-01-22 4:57 GMT-05:00 Jonathan Buzzard <jonathan.buzz...@strath.ac.uk>: > On 22/01/18 03:41, Stephen Ulmer wrote: > >> Harold, >> >> The way I read your question, no one has actually answered it fully: >> >> You want to put the old file system in cold storage for forensic purposes >> — exactly as it is. You want the NSDs to go away until and unless you need >> them in the future. >> >> > Hum, I would have said I did answer it fully even if I didn't go into > detail. The only in my view sensible approach is to do mmexportfs so that > should you need access to the data then you can get to it by reimporting it > using mmimportfs. In the interim you can unmap all the NSD's from the > cluster without causing GPFS to go care in the slightest. > > Otherwise you are doing something that is in my view at the best fool > hardy and more generally down right idiotic. Personally I would outright > refuse to do it without someone else higher up signing a written disclaimer > that I was not responsible should it all go pear shaped. Note that the > mmexportfs takes a few seconds at most to complete, and likewise with the > mmimport. > > I am however somewhat perplexed by the data integrity side of the issue. > If you suspect the data is corrupt in the old file system then having it > around for reference purposes is surely not going to help. What are you > going to do mount it again to find the file is corrupt; how is that going > to help? > > If you suspect that whatever method you used to move the files from the > old file system to the new one may have introduced corruption, then I would > suggest that the best way out of that is to do an rsync with the -c flag so > that it takes an MD5 checksum of the files on both file systems. Once that > is complete you can safely ditch the old file system completely knowing > that you have recovered it as best as possible. You could probably kick a > bunch of rsyncs of in parallel to speed this method up. > > In fact a "rsync -c" would be a gold standard of look it's absolutely the > same on the old and new file systems and remove all doubts about the > transfer introducing corruption. At that point if someone comes and says > your transfer corrupted my files, you can with justification say they where > corrupt in the old file system and I have done my best to transfer them > over. Note if any user was deliberately creating MD5 collisions then they > get everything they deserve in my view, and accidental collisions in MD5 > are about as likely as ħ. > > > JAB. > > -- > Jonathan A. Buzzard Tel: +44141-5483420 > HPC System Administrator, ARCHIE-WeSt. > University of Strathclyde, John Anderson Building, Glasgow. G4 0NG > _______________________________________________ > gpfsug-discuss mailing list > gpfsug-discuss at spectrumscale.org > http://gpfsug.org/mailman/listinfo/gpfsug-discuss >
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