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From:Jed Reynolds Date:January 8 2009 9:19am
Subject:Re: Setup a replication slave without stopping master
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Baron Schwartz wrote:
>> In contrast, InnoDB actually needs to "shut down" to cleanly close its table
>> structures before you can physically copy the filesystem.
>>     
>
> Actually, not true -- an LVM snapshot (or other snapshot) is a great
> way to take a backup of InnoDB.  You just need a truly atomic
> snapshot, and then you can let InnoDB run its recovery routine on the
> snapshot to get back to a consistent state.
>   

Fascinating. From reading the mysql docs, I would never have assumed 
that I was doing the right thing by taking a snapshot of a live innodb 
instance with a flush tables. I will certainly keep this in mind for 
future. My current snapshotting procedure takes between 45s and 90s 
depending on which instance I snapshot, and that's about 20G of data 
that I start copying over. That's not counting time copying anything 
from the snapshotted volume.

>> Why do I leave it firewalled? Because once you start writing to an LVM
>> volume that's been snapshotted, you start copying disk extents like mad,
>> creating a high load condition that can force queries to reach
>> connect_timeout.  I have my connect_timeout set pretty low in my
>> environment.
>>     
>
> That will depend a lot on the workload.
>   

Yes, very pertinent point. I should have qualified how I have a 
write-intensive environment.

I used to just drop the firewall after I restarted mysql, but when my 
application reliability was criticized during my snapshots, I had to 
leave the firewall up until the snapshotted copy was copied off before 
pooling it back in. Luckily I have four servers and there's only rare 
conditions when I need to switch masters. I'm grateful that I have a 
maintenance window for the site, too.

Thank you, Baron!

Jed

Thread
Setup a replication slave without stopping masterClaudio Nanni6 Jan
  • Re: Setup a replication slave without stopping masterJake Maul6 Jan
    • Re: Setup a replication slave without stopping masterBaron Schwartz6 Jan
    • Re: Setup a replication slave without stopping masterClaudio Nanni6 Jan
      • Re: Setup a replication slave without stopping masterJake Maul7 Jan
      • Re: Setup a replication slave without stopping masterBaron Schwartz7 Jan
  • Re: Setup a replication slave without stopping masterJed Reynolds6 Jan
    • Re: Setup a replication slave without stopping masterPaul Choi7 Jan
    • Re: Setup a replication slave without stopping masterBaron Schwartz7 Jan
      • Re: Setup a replication slave without stopping masterJed Reynolds8 Jan
  • RE: Setup a replication slave without stopping masterTheodore Petkantchin7 Jan