Use bs option (size of copy buffer). For example: dd bs=8M if=/root/file of=/dev/sdb8
Good idea would be to use compression to decrease size of backup file dd bs=8M if=/root/file | gzip -9 > /mnt/foobar where /mnt/foobar is /dev/sdb8 filesystem mounted on /mnt/foobar Maybe You could also use some software which would clean up (write with zeroes) unused disk space before backup. Size of compressed file would shrink a lot then. I don't know such software at this moment. And efficiency of such util will surely depend on filesystem You have on /dev/sdb8 Marcin On Wed, 2007-07-25 at 22:52 +0200, Janis Hamme wrote: > Hello from Germany :) > > I want to use the tool dd to create a backup of my hard disk. I have to > identical sata2 hard disks. > > My idea was just to copy them using > dd if=/dev/sda of=/dev/sdb > but the speed was terrible slow. Not more than ~ 15 MB/s. > > In order to find the problem I copied a 1 GB file to partition sdb8. > Speed was about ~ 55 Mb/s. Seems good. > dd if=/root/file of=/dev/sdb8 > > Next I tried to copy the same file to the same partition with the command > dd seek=146818098 if=/root/file of=/dev/sdb > Speed was only ~ 15 MB/s although the result was the same. > It seems to be as slow as copying the whole disk. > > I've made these tests with Knoppix and the Gentoo Live CD. > > My Questions are: > - Why is the speed that slow? > - How can i speed it up without copying each partition. > > Hope you are able to understand my problem (and my english). > > Janis Hamme > > > _______________________________________________ > Bug-coreutils mailing list > [email protected] > http://lists.gnu.org/mailman/listinfo/bug-coreutils _______________________________________________ Bug-coreutils mailing list [email protected] http://lists.gnu.org/mailman/listinfo/bug-coreutils
