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OBS Crash with Replication and Delta Merge

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OBS Crash with Replication and Delta Merge

Postby whittan » Thu May 23, 2013 4:22 pm

Hi,

Just wondering if anyone has come across the OBS crashing, when replication is in unsync or sync mode, AND the server is delta-merging a file?

As a test, I can crash mine everytime, if the OBS is delta-merging, the replication is in sync or unsync and something goes wrong with the replication, ie, loss of connection, or I try to turn it off.

Has plenty of hard drive space, 6gig ram, 6.13.02, but has happened on other versions of software also.
whittan
 
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Postby leemason » Tue Jun 11, 2013 4:37 pm

Not had that particular problem but as far as I am concerned delta merge is completely incompatible with replication unless you have a very high speed link. It simply generates too much data. It looks to me as if the whole delta merged file gets replicated so this could mean hundreds of gigs of log files generated in a very short time completely clogging everything up!

I have some onsite backup servers on customer premises and had to give up using delta merge as replication could never have kept up with the data volumes.

The OBS/RPS link needs a lot of work to my mind and I have spoken to Ahsay about many of the issues including:

1. File copy restarts - when a large file is copying and replication is interrupted the file should continue (like rsync does) from where it left off, and not simply restart from the beginning.
2. If there is an interruption in connection OBS and RPS can have different connections left running. This causes RPS to reject any new connections from OBS. This eventually causes the connection to be reset and replication to restart from the beginning.
3. Delta-Merge causes massive data transfers. To have delta merge work properly the delta merge process should take place on RPS as well as OBS (and not just on OBS by replicating the whole merged file).

etc.
BackupsAnywhere Ltd (http://www.backupsanywhere.com)
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Postby whittan » Tue Jun 11, 2013 5:51 pm

Agreed on all points.

Version 7 is supposed to have multi-threaded replication transfers, should help speed up the small file transfer speeds.

I've got a fast enough connection between the sites to keep up with the traffic, but I have had to pay attention to the amount of room on the system drive that holds the replication logs, fills up fast!

Support has said my particular problem is due to the merging locking the file, and then replication want to access it, it can't, or something like that. They working on a fix.
whittan
 
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Location: New Zealand

Postby leemason » Wed Jun 12, 2013 4:17 pm

That could well be in which case that did not happen with 6.9.4.0 so it could be something new. Multithreading won't help to reduce the massive quantities of data generated by delta merge. I still say it is entirely incompatible with replication if the whole delta merged file has to be replicated (which it looks like to me).
BackupsAnywhere Ltd (http://www.backupsanywhere.com)
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