Are you rsyncing over ssh? If so, get HPN-SSH and use the non-cipher. MUCH faster again :)
On Tue, Jun 18, 2019 at 11:00 PM Bill Wichser <b...@princeton.edu> wrote: > Well thanks for THAT pointer! Using --checksum-choice=none results in > speedup of somewhere between 2-3 times. That's my validation of the > checksum theory things have been pointing towards. Now to get xxhash > into rsync and I think we are all set. > > Thanks, > Bill > > On 6/18/19 9:57 AM, Ellis H. Wilson III wrote: > > On 6/18/19 9:16 AM, Bill Wichser wrote: > >> Stock RH 7 version, rsync-3.1.2-6.el7_6.1.x86_64. We've tried a > >> number of recompiles. gcc, Intel. The only thing between identical > >> compiles was the md4 vs md5. > >> > >> /bin/rsync -lptgoDAH -v --numeric-ids -d --relative --delete > >> --delete-after --files-from=... > >> > >> I'm not asking for help. Just if anyone had attempted to change the > >> algorithm into something much faster. > >> > >> I refer you to this project https://cyan4973.github.io/xxHash/ where > >> there is a table of speeds. Regardless of what anyone might > >> speculate, we are pursuing this route of changing out the algorithm. > >> Maybe it's all for naught. Maybe it isn't. But in a few weeks > >> hopefully we'll have determined. > > > > Very interesting. From the rsync man page: > > > > "Note that rsync always verifies that each transferred file was > > correctly reconstructed on the receiving side by checking a > > whole-file checksum that is generated as the file is transferred, but > > that automatic after-the-transfer verification has nothing to do with > > this option’s before-the-transfer "Does this file need to be updated?" > > check." > > > > So it sounds like you have sufficient churn in large files that the > > checksum validation post-transfer is your bottleneck. Short of hacking > > rsync to use a faster algorithm, your remaining choice is to use the > > --checksum-choice=STR and set it to none, and then perform your own > > hashing out-of-band to check the transferred data using the list you > > have provided via in files-from. This will nerf rsync's ability to do > > delta-transfer, which may be ok depending on the nature of your churning > > files. If your pipes are huge (atypical for DR), your CPU is weak, and > > your churning data is mostly completely new or completely changed files, > > --checksum-choice=none may work very well for you. > > > > Best, > > > > ellis > > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > https://beowulf.org/cgi-bin/mailman/listinfo/beowulf > -- Dr Stuart Midgley sdm...@gmail.com
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