[DRBD-user] Problems after upgrade 8.2.0 to 8.3.0

John Du jjohndu at gmail.com
Mon Feb 9 22:04:37 CET 2009

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Lars Ellenberg wrote:
> On Mon, Feb 09, 2009 at 10:35:44AM -0800, John Du wrote:
> [...]
>>> 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.
>> 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.
> 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.
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.
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