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<div class="moz-cite-prefix">On 13/06/13 05:29, Robinson, Eric
wrote:<br>
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<div dir="ltr" align="left"><span class="622012104-13062013"><font
color="#0000ff" face="Calibri">I really appreciate
everyone's input but everyone misunderstood the question I
was really asking. It's my fault for mentioning rsync. I
fully understand the difference between how rsync works and
how drbd works. We use them both all the time. But the real
question is more high level. We have been told that even if
you stop the mysql service, you still cannot backup an
innodb database by simply copying the files from one server
to another. We have been told that the mysql service will
not start properly on the new server even if you make a 100%
exact copy of all the files from the old server. If that is
true, I don't understand how using drbd can work with innodb
tables, since it basically just makes a copy of the files to
another server. Am I asking the question right?</font></span></div>
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<p style="MARGIN: 0in 0in 0pt" class="MsoNormal" align="left"><span
style="FONT-FAMILY: Tahoma; FONT-SIZE: 10pt"><font size="3"
face="Calibri">--<br>
</font></span><span style="FONT-FAMILY: Tahoma; FONT-SIZE:
10pt"><font size="3" face="Calibri">Eric Robinson<br>
</font></span></p>
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<br>
For what it's worth, we run MySQL+InnoDB on DRBD and use
Heartbeat+Pacemaker for failover between nodes at different sites.
This supports our Moodle VLE which is an important part of our
course provision. As yet we have had no problems. We also use <b>mysqldump</b>
to back up databases.<br>
<br>
To quote from Wikipedia:<br>
<br>
"
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<span style="color: rgb(0, 0, 0); font-family: sans-serif;
font-size: 13px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
19.1875px; orphans: auto; text-align: left; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
background-color: rgb(255, 255, 255); display: inline !important;
float: none;">InnoDB recovers from a crash or other unexpected
shutdown by replaying its logs"<br>
<br>
These logs, by nature of the fact they're on a DRBD device, will
be identical on both nodes, so if, say, node-A fails, node-B can
assume Primary role for the DRBD device and mysql can start up,
replaying its logs to may sure the data is up-to-date. <br>
<br>
I think whoever told you mysql would not start properly was
possibly referring to what would happen if you simply copied all
the files (with, for instance, rsync) whilst the database was
active.<br>
</span>
<pre class="moz-signature" cols="120">--
Paul Walsh
Head of Unix/Linux Systems Services,
Corporate ICT,
Birmingham City University,
City North Campus, Perry Barr,
BIRMINGHAM B42 2SU, UK
Tel: +44 (0)121 331 5708
Fax: +44 (0)121 356 2875
Mobile: +44 (0)7974 150 421
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