Thanks a lot for that. I'm not experienced in reading the output of dtrace, but I'm pretty sure that dedup was the cause here, as I disabling it during the transfer, immediately raised the transfer speed to ~100MB/s.
Thanks for the article you linked to — it seems my system would need about 16GB RAM for dedup to work smoothly in my case... On Fri, Sep 24, 2010 at 11:10 PM, David Blasingame Oracle < david.blasing...@oracle.com> wrote: > How do you know it is dedup causing the problem? > > You can check to see how much is by looking at the threads (look for ddt) > > mdb -k > > ::threadlist -v > > or dtrace it. > > fbt:zfs:ddt*:entry > > You can disable dedup. I believe current dedup data stays until it gets > over written. I'm not sure what send would do, but I would assume the new > filesystem if dedup is not enabled would not have dedup'd data. > > You might also want to read. > > http://blogs.sun.com/roch/entry/dedup_performance_considerations1 > > As far as the impact of <ctrl-c> on a move operation, When I do a test to > move a file from one file system to another an <ctrl-c> the operation, the > file is intact on the original filesystem and on the new filesystem it is > partial. So you would have to be careful about which data has already been > copied. > > Dave > > On 09/24/10 14:34, Thomas S. wrote: > > Hi all > > I'm currently moving a fairly big dataset (~2TB) within the same zpool. Data > is being moved from a dataset to another, which has dedup enabled. > > The transfer started at quite a slow transfer speed — maybe 12MB/s. But it is > now crawling to a near halt. Only 800GB has been moved in 48 hours. > > I looked for similar problems on the forums and other places, and it seems > dedup needs a much bigger amount of RAM than the server currently has (3GB), > to perform smoothly for such an operation. > > My question is, how can I gracefully stop the ongoing operation? What I did > was simply "mv temp/* new/" in an ssh session (which is still open). > > Can I disable dedup on the dataset while the transfer is going on? Can I > simply Ctrl-C the procress to stop it? Shoul I be careful of anything? > > Help would be appreciated > > > > > -- > > > > >
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