DSM-G600, DNS-3xx and NSA-220 Hack Forum

There are other threads that discuss rsync and disk copy speeds.

But you are comparing apples (rsync) and oranges (file copy).

Rsync is a file synchronization system and protocol designed to sync files across networks, often over low bandwidth connections.  It is not designed or optimized to simply copy files, even when the copy is local. 

Even when you run rsync with a local source and a local destination, rsync will start two additional rsync processes, one to send the source files, and the other to receive the files.  The file data gets sent over a pipe between the two processes using IPC (inter process communication) and there is probably a fair amount of "difference processing" going on in rsync, as rsync analyzes each block of the files to determine which blocks of the file need to be transferred.  The whole point of rsync is to minimize the data going over the IPC connection (local or not) even at the expense of doing a lot of work to get that minimization.  Usually rsync is run between two different machines, with the IPC going over an external network.

A simple file copy, even over a LAN, involves much less overhead.

A lot of people who use rsync to do drive-to-drive copies like this often do an initial manual copy of any new files on the source disk to the destination disk, precisely to avoid the initial slow rsync transfer.

But once the files are established in both places, rsync is very quick and efficient in resolving any small incremental differences in the files.

So, yes, the speeds that you are seeing with rsync are nominal when you are doing an initial sync.  If you run rsync again with little or no new files, your effective rsync bandwidth as reported by rsync would be extremely high.

I have somewhat similiar io running rsync between disks.

root@alice:~# iostat -m
Linux 2.6.32-5-orion5x (alice)     04/28/2011     _armv5tel_    (1 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          31.16    0.00   56.12    1.33    0.00   11.38

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
mtdblock0         0.00         0.00         0.00          0          0
mtdblock1         0.00         0.00         0.00          0          0
mtdblock2         0.00         0.00         0.00          0          0
mtdblock3         0.00         0.00         0.00          0          0
mtdblock4         0.00         0.00         0.00          0          0
sda               1.68         0.02         0.00       5489        844
sdb              15.07         0.00         3.63        305    1114814
sdc              34.96         3.63         0.02    1113205       4716

Sure, any new file is going to be copied over at the same rate achieved by the initial rsync.  Rsync checksums the files during transfer for validating the transfer, which takes longer.  It also checks that the rest of the fileset is in sync, and that's what is meant by the effective sync rate.

If you had a huge file already on the source and destination and the source had a one-byte change in it, rsync would update the file on the destination much faster than it would take to copy the entire file over.  This also contributes to a high effective sync rate.  And this is the type of case where rsync shines, especially over a remote network connection.

If you are just plunking down new half-GB files into the source periodically, rsync will take some time to copy them over.  And that's not the optimum use case for rsync.  This shouldn't be a huge concern since rsync should just do its thing in the background and not bother anything else.  If getting the files synced with rsync is too slow for you, then perhaps rsync is not the tool for the data you are managing.

In my case, as an example, I rsync a lot of small files that change frequently over a remote network connection. So, rsync is ideal.  I also sync media files like yours that don't ever get modified, but may get deleted or moved occasionally.  Rsync is not the greatest for these files, but I still use it for its convenience and since my DNS-323 is a Server, I don't care too much about how long it takes.