DO NOT REPLY [Bug 7349] New: Add --limit-time=<seconds> and --fit-time=[seconds] options

samba-bugs at samba-bugs at
Sun Apr 11 03:58:54 MDT 2010

           Summary: Add --limit-time=<seconds> and --fit-time=[seconds]
           Product: rsync
           Version: 3.1.0
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P3
         Component: core
        AssignedTo: wayned at
        ReportedBy: bugzilla.samba.simon at
         QAContact: rsync-qa at

More (cheaper) bandwidth is available between 2am and 6am, so it is the ideal
time to run rsync for backup purposes. However, in order to allow the maximum
possible time for rsync to complete it must be started at 2am even if it would
only take a shorter period of time (e.g. 2 hours). If there are a lot of users
(of an ISP) doing this then there will be a large undesireable spike at 2am.

Ideally they would all schedule times so they don't overlap but this is
impractical. Instead, rsync could automatically reduce the bandwidth limit so
that the transfer takes the full time. This would require determining the size
of all files to be transferred in advance and then adjusting the bandwidth
limit based on remaining time.

--limit-time would limit the maximum duration of the process
--fit-time would lower the --bwlimit (which may not be set; this will
dynamically change if it's not going fast enough) so that the transfer takes
the intended time

The default for --fit-time should be 95% of the --limit-time, allowing some
time for the inexact nature of adjusting bandwidth dynamically so that the
transfer can complete successfully. Transfers should never exceed --bwlimit
even if the time would not be met. Compression is likely to complicate the
situation so that transfers get progressively slower, but the assumption is
that these files are already compressed so this will not be used.

Any checksum-based options would need to be disabled unless they could avoid
reading files twice (once at the start and once at the transfer stage). Partial
transfers and appending are probably an implicit requirement of limiting the
transfer time. Currently I have a cron job kill rsync at 6am.

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