Hi, Lothar Schilling wrote: > Fast enough... > dd if=/daten/testfile bs=1G oflag=direct of=/daten/testfile2 > 10737418240 Bytes (11 GB, 10 GiB) kopiert, 72,7297 s, 148 MB/s
So this is sufficiently fast, but cp /daten/testfile /daten/testfile2 lasts 2000 seconds ? > dd if=/daten/testfile of=/dev/null > 10737418240 Bytes (11 GB, 10 GiB) kopiert, 36,6887 s, 293 MB/s It is not about the number of read/write operations. (How fast is bs=1G on the second try ?) ------------------------------------------------------------------------ It is also not about the filesystem and its health status. So where could be any difference ? dd is an i/o dinosaur. It performs read/write without much mind. cp uses a centralized copy facility by a function named "copy ()". This facility makes much ado about sparse files: https://sources.debian.org/src/coreutils/8.30-3/src/copy.c/#L387 https://sources.debian.org/src/coreutils/8.30-3/src/copy.c/#L224 man cp says: By default, sparse SOURCE files are detected by a crude heuristic and the corresponding DEST file is made sparse as well. That is the behav‐ ior selected by --sparse=auto. Specify --sparse=always to create a sparse DEST file whenever the SOURCE file contains a long enough sequence of zero bytes. Use --sparse=never to inhibit creation of sparse files. So i'd try cp with --sparse=never in order to see whether it then resembles the behavior of dd. Have a nice day :) Thomas
