Re: troubleshooting slow I/O performance.

From: Mladen Gogala <>
Date: Tue, 8 May 2018 23:14:20 -0400
Message-ID: <>

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:
> Anything further is related to this drill-down outcome :-)
> Best Regards
> Stefan Koehler
> Independent Oracle performance consultant and researcher
> Website:
> Twitter: _at_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

Received on Wed May 09 2018 - 05:14:20 CEST

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