Problems with journal?

[Ivan Voras]

Giulio Ferro wrote:
> Giulio Ferro wrote:
>> I'm experiencing very serious delay issues in 2 production servers.
> [...]
>>
>> I hope any of you can help me look in the right direction, and point
>> me to any further tests to try or tunable
>> to set...
>>
>> Thanks in advance.
>>
> 
> I didn't receive any answer to this, so I'm guessing ufs journal
> is abandoned or there is no interest in supporting it in production
> environment.
> Anyway I removed it from my servers and reverted to standard UFS,
> so the problems disappeared.  I also tried zfs (the only other journaled
> filesystem available on freebsd). I didn't experiences the hanging behavior
> I did with journaled ufs, but it's considerably slower than standard ufs
> (1/2 slower writes, 1/10 slower reads)...

Both gjournal and ZFS are still "experimental" as far as stability and
performance is concerned (actually, I have the feeling that gjournal
itself is simple enough to be ok but it exposes timing problems with
UFS...), but you might help by giving more information about your problem:

* send output from top (with "S" mode) and vmstat ("vmstat 1") when you
experience your slowdown problem
* create a kernel core dump (see
http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug.html#KERNELDEBUG-OBTAIN
and
http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-online-ddb.html
, enter "call doadump" on the online debugger prompt) when your problem
starts.
* attach a debugger to the kernel dump, record and send output of "ps",
"show pcpu", "show allpcpu", "show locks", "show alllocks", "show
lockedvnods" and "alltrace."

These are just generic tips, I don't have an idea what might cause your
problems (so some of the information I requested might be useless, but
better to send as much as possible; maybe someone will see something
interesting).

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