rsync - Sep 2018 - [Bug 13609] New: rsync can be crazy slow on os x 10.13.6 when copying via usb drives

https://bugzilla.samba.org/show_bug.cgi?id=13609

            Bug ID: 13609
           Summary: rsync can be crazy slow on os x 10.13.6 when copying
                    via usb drives
           Product: rsync
           Version: 3.1.3
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P5
         Component: core
          Assignee: wayned at samba.org
          Reporter: mvolaski at aecom.yu.edu
        QA Contact: rsync-qa at samba.org

I am copying files from one USB SATA drive to another connected to a Mac Pro
via USB 3. Rsync should be able to copy approaching 100 MB/second, but it never
copies anywhere near this speed and for a few files, it's so slow as to
almost
be stalled, averaging near 131KB/second. The OS is Mac OS 10.13.6 and the rsync
is provided via homebrew.

The command being used is as follows
/usr/local/bin/rsync --acls --archive --delete
--exclude-from=/usr/local/etc/backupignore --sparse --verbose --progress
--xattrs /Volumes/externalhd/ /Volumes/backuphd/external/

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--- Comment #1 from mvolaski at aecom.yu.edu ---
The sparse option is triggering this slowness. Without it, rsync runs super
fast.

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--- Comment #2 from mvolaski at aecom.yu.edu ---
I should also mention the file being copied so slowly is a Virtualbox virtual
disk file.

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--- Comment #3 from roland <devzero at web.de> ---
what is the source and what is the remote filesystem ?

what does iostat tell on the source and the destination?


what's the size of the sparse files and how much of data is
"inside" ?

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--- Comment #4 from Dave Gordon <dg32768 at zoho.eu> ---
How about using truss/strace/whatever the OSX equivalent is to get a count of
all system calls made, when run with and without the --sparse option. Total
time on each type of call would be useful too.

If you find that --sparse results in ten times as many write(2)s, that might be
a useful clue!

BTW remember there is a bug that is triggered by using --sparse and
--preallocate (and possibly --inplace) together. See
https://bugzilla.samba.org/show_bug.cgi?id=13320#c1 for details.

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