(Not retransferring files deleted from destination)

Ed W lists at wildgooses.com
Fri Jun 26 15:21:36 GMT 2009

Low, Alex wrote:
> Hi Matt,
> Phew ! you were quick, and it's very much appreciated.
> Ok.
> We have three Solaris servers, and we have an Oracle database running on
> each of them, 1 Primary (prod) and 
> 2 standbys (one 24 hours behind Prod & and the other 4 hours behind
> Production).
> The Arch logs are shipped from Prod Primary automatically, firstly, to
> the 24-hour Standby as they are generated in Prod.  From there, the same
> arch logs are copied to the 2nd server hosting the 2nd standby using
> rsync.
> On the 2nd standby server, the arch logs are deleted (for space
> management)
> once the 4-hour-behind-Prod standby database has been rolled forward.  
> So, we have created ourselves a situation with arch logs where the 2nd
> standby server Has LESS arch logs than the 1st standby.  
> At present, rsync re-transfers those arch logs which have been removed
> from
> the 2nd standby.  This is undesirable because disk space is being
> consumed again unnecessarily.  So, we are hoping that  rsync can be
> programmed via soft switches that arch logs from the 1st standy host,
> once transferred for the first time, will NOT be re-transferred as the
> 2nd standby has rolled forward the logs and they are no longer needed.
> Hope you can suggest an rsync solution which will help overcome our
> issue
> As outlined above.
> Thanks very much.
> Cheers.
> Alex.
> -----Original Message-----
> From: Matt McCutchen [mailto:matt at mattmccutchen.net] 
> Sent: Monday, 22 June 2009 9:47 AM
> To: Low, Alex
> Cc: rsync at lists.samba.org
> Subject: Re: (Not retransferring files deleted from destination)
> On Mon, 2009-06-22 at 09:24 +0800, Low, Alex wrote:
>> We do have a situation now where we need rsync to transfer the files
>> once only from the source directory.  Please let me briefly explain
>> using a simple generic exmple:
>> 1. At t0, we transfer f0 location A to location B
>> 2. At t1, 10 new files are added to Location A
>> Therefore, rysnc faithfully transfers all 10 new files to location B
>> At location B, we now have f0 to f10.
>> 3. At t2, f0 to f3 are deleted from location B, and we don't ever want
>> the deleted files to be copied again from location A
>> 4. At t3,  rysnc waits up, transfers files f0 and f10 again plus any
>> new files that may have been added.
>> So, at location B, we end with the deleted files f0 to f3 again.
>> Can you please think of a way we can soft-switch rsync NOT to do step
>> 4 above ?
> As a stateless one-way mirroring tool, rsync doesn't support that
> (unless you count --remove-source-files).  If you could provide some
> more insight into your workflow, I might be able to come up with a
> suitable alternative approach.

I love rsync, but I recently discovered unison and for some tasks it 
works better.  In particular it is designed to track changes on both 
sides and can spot the difference between something deleted and not yet 
copied.  Perhaps give it a whirl with the options set to only transfer 
left to right (ie don't send the deletes back to source)

Good luck

Ed W
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