Dne 31.3.2011 02:27, Stuart D. Gathman napsal(a): > On Wed, 30 Mar 2011, Ray Morris wrote: > >>> 1..how to pipe two copy together >> >> This is what I use after some experimenting. I've found >> it's often far faster than the more obvious use of dd: >> >> nice -5 dd if=/dev/clones/from bs=64M iflag=direct | >> dd of=/dev/scratch/to bs=64M oflag=direct >> >> I use 64 MB extents. For smaller extents, a matching dd >> block size might be good. > > Thanks for that recipe. It ought to be in lvm2 as an lvcopy utility > (dynamically determining extent size, etc). > Isn't this already done in a better way by 'dd' using 'zero' copy mechanism ?? (assuming it is already using either 'mmap()' -> 'write()' or 'splice()' as your proposed piped copy is doing a lot of pointless memory copies and cache trashing. If it's still faster - then your kernel setting for buffering are most probaly not tuned for the best performance. Zdenek _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
