Re: troubleshooting slow I/O performance.
- From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Tue, 8 May 2018 23:14:20 -0400
On 05/08/2018 04:13 AM, Stefan Koehler wrote:
Hello Chris,
at first you need to identify where the time is spent in the whole I/O stack
(e.g. I/O scheduler, SCSI, etc.).
For example you can do that with blktrace on Linux:
http://www.fis.unipr.it/doc/blktrace-1.0.1/blktrace.pdf
Anything further is related to this drill-down outcome :-)
Best Regards
Stefan Koehler
Independent Oracle performance consultant and researcher
Website: http://www.soocs.de
Twitter: @OracleSK
There is rarely need to lose time by doing blktrace. If disks are too
slow, the ONLY real answer are faster disks. I used to play with IO
elevators, read ahead, systemtap and stuff like that, but the truth is
that whenever I delved into that stuff, nothing useful ever came out of
it. When IO is too slow, the faster disks are the only solution. No
amount of tuning will turn a Ford Taurus into a Ferrari. Storage
configuration is usually planned ahead of configuring the database. It
may even be prudent, I apologize for using harsh language, to do some
testing ahead of building the whole cluster. This sounds like the
configuration done by the most interesting DBA in the world: the one who
doesn't test his stuff often, but when he does so, he does it in production.
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
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