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Lars Ellenberg wrote:
<blockquote cite="mid:20090209201717.GB11714@barkeeper1-xen.linbit"
type="cite">
<pre wrap="">On Mon, Feb 09, 2009 at 10:35:44AM -0800, John Du wrote:
[...]
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">8.0.12 (2008-04-24) was the first release that could switch off this
additional reliability feature again, as it turned out that the
"better", more "advanced", IO subsystem you have, the worse the
performance impact is when turning on barriers/flushes.
the options to do so are "no-disk-flushes" (backing store),
"no-md-flushes" (meta data store).
in the 8.2 series, 8.2.6 (2008-05-30) is the first release
to support these keywords to switch off these additional
reliability features again.
8.2.7, and 8.3.0 again add some more advanced handling
for additional performance while maintaining reliability
when running on volatile caches.
again, these features can be switched of.
They should only be switched off if you run on a "safe" device
(non-volatile, battery backed cache -- or no cache at all).
the important additional switch now is "no-disk-barrier".
see also "man drbd.conf"
all of this has _nothing_ to do with whether "iostats" shows
statistics for drbd or not.
</pre>
</blockquote>
<pre wrap="">Thank you Lars for your detailed explanation. I'll try the parameters
you mentioned above. As I mentioned in my original message the process
queue reaches 100 on this node when running 8.3 and it is under 1 with
8.2.0.
I still do not understand why iostat only shows DRBD devices on this
particular node with 8.2.7 and 8.3.0 but not other nodes with the same
hardware, same Linux Kernel and same DRBD version.
</pre>
</blockquote>
<pre wrap=""><!---->
io stats accounting was introduced only in drbd-8.0.12 respective 8.2.6.
if you don't see drbd in iostats, you probably use an older DRBD version.
</pre>
</blockquote>
I obviously did not make myself clear. We were running 8.3 on six
nodes and only this node showed DRBD in iostat and only this node was
having the problem I reported. I reverted to 8.2 on this node to make
our production going.<br>
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