Bacula-users

Re: [Bacula-users] 1 second Network glitch kills Windows backups

2016-07-01 16:32:04
Subject: Re: [Bacula-users] 1 second Network glitch kills Windows backups
From: Kern Sibbald <kern AT sibbald DOT com>
To: Josh Fisher <jfisher AT pvct DOT com>, bacula-users AT lists.sourceforge DOT net
Date: Fri, 1 Jul 2016 22:30:31 +0200
Hello,

In general, the TCP/IP protocol that Bacula uses is extremely tolerant, 
and should retry sending packets quite a number of times before finally 
giving up.  It is designed to tolerate a significant number of dropped 
packets.  However, then there are two things that enter to screw this 
up: 1. network switches which do not follow internet rules at all (i.e. 
they are very fast to drop idle connections, even if you have explicitly 
set the network to survive idle periods as Bacula does); 2. Windows 
which does not seem to follow quite a few Internet rules.  The two put 
together mean that especially with on Windows machines, network 
disruptions are annoyingly frequent.

Bacula was designed with the concept that the Internet never loses 
packets and that it is highly tolerant -- given the above two problems, 
maybe this was a bad choice.  However, the result of that decision is 
that if the line drops, Bacula has no idea what reached and what did not 
reach the other side, and so it is not currently possible for it to 
reconnect and resume where it left off.

Best regards,
Kern

On 07/01/2016 03:43 PM, Josh Fisher wrote:
> On 7/1/2016 1:26 AM, Craig Shiroma wrote:
>> Hello All,
>>
>> Is there a way in Bacula to prevent something like a 1 or 2 second
>> network glitch from cancelling Window Server backups? RHEL backups
>> seem to survive these episodes with no problems.
>>
> Bacula expects DIR-to-FD and FD-to-SD TCP connections to persist for the
> duration of a job. If either is dropped it will cause the job to cancel.
> As a result, Bacula is not very tolerant of network problems. Since it
> appears to be the Windows Server machines dropping the connection due to
> the glitch, if there is a solution it will be in the Windows networking
> config, possibly in the NIC's driver settings. Perhaps RHEL is more
> tolerant of the glitch or perhaps it is a hardware difference in the
> NICs. Nevertheless, in general such network glitches cause problems for
> Bacula regardless of OS.
>
>
>
>> Respectfully,
>> Craig
>>
>
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