what is the default speed in rsync to send from local to remote machine?

Question

I want to know the default speed of rsync command to send data from local machine to remote machine. Is that depend on network or rsync has default speed is set for rsync command.

Solution 1

The default speed depends on the network, and on the system.
If not explicitly asked for, rsync will try to use all the available bandwidth.

Nevertheless you can read a speed value higher then the physical bandwidth of your connection because the counts of the speedup value is probably made dividing the total amount of data for the used time; note the "total amount of data" and not the "total amount of data transferred". This is even more evident when you do a dry-run with the -n option specified to perform a trial run that will not make any change.

Indeed rsync can skips files or part of the files in the transfer operation when it is not needed to update them following the current options.

Rsync finds files that need to be transferred using a "quick check" algorithm (by default) that looks for files that have changed in size or in last-modified time. Any changes in the other preserved attributes (as requested by options) are made on the destination file directly when the quick check indicates that the file’s data does not need to be updated.

Option that can affect the normal use (see below) are

--bwlimit=RATE          limit socket I/O bandwidth
                        Note that since rsync can also be run as a daemon
                        this option is accepted in both cases client and demon.


-W, --whole-file        With this option rsync’s delta-transfer algorithm is not
                        used and the whole file is sent as-is instead.  

About -W

The transfer may be faster if this option is used when the bandwidth between the source and destination machines is higher than the bandwidth to disk (especially when the "disk" is actually a networked filesystem). This is the default when both the source and destination are specified as local paths, but only if no batch-writing option is in effect.

Note: it is always possible (even if not probable) that your system is limiting the bandwidth for the processes (see for example [1]) or the host system in the case of VirtualBox or Windows+Cygwin is putting some limits or delay due to different operations (sniffing, antivirus...)

Solution 2

I don't think rsync have a default speed. Most of the time rsync is used with ssh and speed over scp will be same as rsync

Comments

[Larssend]

Rsync doesn't have a speed setting, but it has an option to limit maximum bandwidth usage (the --bwlimit option).

[LOKESH]

I know the --bwlimit option but I want ot know whether speed is improve with --bwlimit set to 25000 i.e.(25 mb/s)?

[Larssend]

'Limiting speed' is obviously the exact opposite of ' improving speed.'

[Hastur]

Hi Lokesh, in the name of the parameter is hard-coded BandWidthLIMIT (--bwlimit), and limit is the opposite of improve :-). In some sense if there is a previous and smaller limit it that be can interpreted (or it can act) as __extend speed__(bandwidth). The only limit that can fall in this case is on the deamon, but for what I know it is not the default behaviour. BTW, try to post the real question you have in order to avoid cases as the XYproblem and to have the answer to the question that you are really looking for.

[LOKESH]

can you give me more discription about windows+cygwin for delay in rsync

[Hastur]

With Cygwin you share part of the windows HD with the Cygwin environment. Even if you use rsync from the Cygwin commandline, those files are always subject to the control of the hosting operative system. If in windows there is an antivirus active (as it is usual) those files will be scanned by it (if they have to, of course). If a temporary file is created, even this one can be scanned by the antivirus... If there is some utility that organizes the filesystem it can decide to change their position... and so on...

[Hastur]

Read from the manual of rsync the option --inplace and --append. They can change the overall speed of the transfer, even more if there is an antivirus on the windows destination...

[James Shewey]

I'm not sure if rsync can't or won't use all available bandwidth, but rsync will try to use all the available bandwidth is not true. Don't believe me? Compare performance of rsync with bbcp.

[Hastur]

@JamesShewey rsync differs from bbcp. bbcp is more similar to scp. BTW I trust that in SLAC/cern collaboration they developed tools efficient with huge data transfer (we have internet thanks to the particle physics needs...) and it is a nice spot to a (still) less known tool...