RE: [CentOS] Painfully slow NetApp with databas

David Ross Geek4AllSeasons at hotmail.com
Thu Nov 6 21:32:26 UTC 2008



> -----Original Message-----
> From: centos-bounces at centos.org [mailto:centos-bounces at centos.org]On
> Behalf Of Mindaugas Riauba
> Sent: Thursday, November 06, 2008 3:45 AM
> To: nahant-list at redhat.com; CentOS at centos.org
> Subject: [CentOS] Painfully slow NetApp with databas
> 
>   We have long running problem with NetApp filers. When we connect
> server to the filer sequential read performance is ~70MB/s. But once
> we run database on the server seq read performance drops to ~11MB/s.

There many factors which impact database i/o performance. You are comparing two probably dissimilar i/o paths. Configuration differences (disk, controller, connection, kernel parameters) may be part of the problem.

Physical vs. logical sequence, i.e. disk head movement, is particularly significant for sequential access. Throughput increases of 200% to 500% are not uncommon after packing (dump/restore) of a large table.

The database translates and theoretically optimizes sql statements generating query plans. They should be examined to determine if there are doing what is expected.

> That's happening with two servers. One is running Oracle another -
> MySQL. During speed tests database load is very light (less than 1MB/s
> of reads and writes). During the tests NetApp was serving only these
> two servers.
> 
>   What could be causing such slowdown and overall slow read
> performance? Writes are fast >100MB/s.
> 

Database performance data is another good source of diagnostic info. It can help pinpoint query plan problems.

This article may help you put all the pieces together. It is one of the best I have found:

http://www.miracleas.com/BAARF/oow2000_same.pdf

The author is Juan Loaitza from Oracle.


Hope some of this helps.

david



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