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Re: I have a quick question about exporting or dumping a database.

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On 08/10/2012 11:34 AM, Florian Weimer wrote:
> * jeff:
>
>> I have a server running Citadel which uses Berkeley DB on the back end
>> and I am trying to transfer the VM that is running it to a different
>> server and when I just copy the virtual hard drive and load it the
>> database is corrupt and cannot be fixed.
>
> This is odd.  Are you copying a volume which is being written to?  If
> you copy a read-only snapshot, it should work.
>

Yes it is being written to right now because it is production. I will 
see about scheduling some downtime for this.

>> 1. How long should it take to dump a database? Mine is about 7.4 GB
>> with about 200 MB of log files right now.
>
> That mostly depends on fragmentation.  About an hour would not be
> entirely unheard of.

Only an hour, that is not a problem but the dumps that I have attempted 
have taken 8-10 hours and either never finished or came up with an error.

>
>> 2. What is the best way to transfer the database to a different
>> system? I would prefer a method that does not involve downtime as this
>> is a production email system.
>
> You need to make the database read-only at one point, otherwise some
> writes will be lost.  And if you change versions of Berkeley DB, you
> have to perform environment recovery, which also requires downtime.

I have reason to believe that I am pushing the limits of the hard drive 
IO even though the drives I am using are not exactly slow, but the 
results of trying to copy does not seem to be effected by other virtual 
machines running on that system. From other tests that I have done I 
have verified that memory, and CPU are not being used much at all, but 
the IO on the hard drive, mostly waiting for random seeks might be 
causing problems. I have also noticed what appears to be some possible 
corruption with other VMs which from what I can tell is affected by the 
drive IO since moving to the new system with a larger RAID array seems 
to have fixed the problems.

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Thread

I have a quick question about exporting or dumping a database. jeff <thexder1@gmail.com> - 2012-08-09 19:32 -0700
  Re: I have a quick question about exporting or dumping a database. Florian Weimer <fw@deneb.enyo.de> - 2012-08-10 20:34 +0200
    Re: I have a quick question about exporting or dumping a database. jeff <thexder1@gmail.com> - 2012-08-10 13:20 -0700
      Re: I have a quick question about exporting or dumping a database. Florian Weimer <fw@deneb.enyo.de> - 2012-08-10 22:42 +0200

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