Copy or rsync command

Question

The following command is working as expected     cp -ur  home abc    mnt windowsabc    Does rsync has any advantage over it  Is there a better way to keep to backup folder in sync every 24 hours

User · Answer

The command as written will create new directories and files with the current date and time stamp, and yourself as the owner. If you are the only user on your system and you are doing this daily it may not matter much. But if preserving those attributes matters to you, you can modify your command with

cp -pur /home/abc/* /mnt/windowsabc/

The -p will preserve ownership, timestamps, and mode of the file. This can be pretty important depending on what you're backing up.

The alternative command with rsync would be

rsync -avh /home/abc/* /mnt/windowsabc

With rsync, -a indicates "archive" which preserves all those attributes mentioned above. -v indicates "verbose" which just lists what it's doing with each file as it runs. -z is left out here for local copies, but is for compression, which will help if you are backing up over a network. Finally, the -h tells rsync to report sizes in human-readable formats like MB,GB,etc.

Out of curiosity, I ran one copy to prime the system and avoid biasing against the first run, then I timed the following on a test run of 1GB of files from an internal SSD drive to a USB-connected HDD. These simply copied to empty target directories.

cp -pur    : 19.5 seconds
rsync -ah  : 19.6 seconds
rsync -azh : 61.5 seconds

Both commands seem to be about the same, although zipping and unzipping obviously tax the system where bandwidth is not a bottleneck.

User · Answer

rsync is not necessarily more efficient  due to the more detailed inventory of files and blocks it performs  The algorithm is fantastic at what it does  but you need to understand your problem to know if it is really going to be the best choice   On a very large file system  say many thousands or millions of files  where files tend to be added but not updated   cp -u  will likely be more efficient  cp makes the decision to copy solely on metadata and can simply get to the business of copying   Note that you might want some buffering  e g  by using tar rather than straight cp  depending on the size of the files  network performance  other disk activity  etc  I find the following idea very useful   tar cf -     tar xCf directory -   Metadata itself may actually become a significant overhead on very large  cluster  file systems  but rsync and cp will share this problem   rsync seems to frequently be the preferred tool  and in general purpose applications is my usual default choice   but there are probably many people who blindly use rsync without thinking it through

User · Answer

For a local copy  the only advantage of rsync is that it will avoid copying if the file already exists in the destination directory   The definition of  already exists  is  a  same file name  b  same size  c  same timestamp    Maybe same owner group  I am not sure      The  rsync algorithm  is great for incremental updates of a file over a slow network link  but it will not buy you much for a local copy  as it needs to read the existing  partial  file to run it s  diff  computation   So if you are running this sort of command frequently  and the set of changed files is small relative to the total number of files  you should find that rsync is faster than cp    Also rsync has a --delete option that you might find useful

User · Answer

It s not really a question of what s more efficient   The commands  rsync   and  cp  are not equivalent and achieve different goals   1- rsync can preserve the time of creation of existing files   using -a option  2- rsync will run multiprocess and transfer using either local sockets or network sockets   i e  fork itself into multiple processes  3- The multiprocessing  and threading will increase your throughput when copying large number of small files  and even with multiple larger files   So bottom line is rsync is for large data  and cp is for smaller local copying   MB to small GB range    When you start getting into multiple GB or in the TB range  go with rsync  And of course network copies  rsync all the way

User · Answer

Keep in mind that while transferring files internally on a machine i e not network transfer  using the -z flag can have a massive difference in the time taken for the transfer   Transfer within same machine  Case 1  With -z flag      TAR took  9 48345208168     Encryption took  2 79352903366     CP took   5 07273387909     Rsync took   30 5113282204  Case 2  Without the -z flag      TAR took  10 7535531521     Encryption took  3 0386879921     CP took   4 85565590858     Rsync took   4 94515299797

User · Answer

Especially if you use a copy-on-write filesystem like BTRFS or ZFS  rsync is much better   I use BTRFS  and I have this in my    bashrc   alias cp  rsync -ah --inplace --no-whole-file --info progress2    The important flag here for CoW FSs like BTRFS is --inplace because it only copies the changed part of the files  doesn t create new for small changes between files inodes  etc  See this

User · Answer

if you are using cp doesn t save existing files when copying folders of the same name  Lets say you have this folders    myFolder   someTextFile txt   someOtherFolder    myFolder     wellHelloThere txt   Then you copy one over the other   cp  someOtherFolder myFolder  myFolder   result    myFolder   wellHelloThere txt   This is at least what happens on macOS and I wanted to preserve the diff files so I used rsync

User · Answer

Rsync is better since it will only copy only the updated parts of the updated file  instead of the whole file  It also uses compression and encryption if you want  Check out this tutorial

[rsync] Copy or rsync command

Examples related to rsync

Examples related to cp