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From: "V.99" <v DOT 99 AT seznam DOT cz>
Subject: mysql - poor performance when restoring from large mysqldump backup
Message-ID: <55907088.70901@seznam.cz>
Date: Mon, 29 Jun 2015 00:09:12 +0200
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Hello.

I am trying to restore a backup of our database in order to examine the 
data state three weeks ago.
Backup is 1GB large SQL text file created by mysqldump.
After many attempts I found this:
Processing of backup file runs fluently in the beginning, several tables 
are successfully restored, including table event_log 3x10e6 row big.
Processing hangs after cca one hour of run during insert-s to table 
student_grade - this is approx 6x10e6 row big. (Exact place differs in 
every attempt.)
Mysqld process is running as before: 13%CPU, 187MB RAM, but HDD activity 
is now very low. Open connection to mysqld is not possible. I was 
waiting that mysqld will recover more than six hours, but the situation 
has not improved.
All this occurs on my workstation Intel(R) Core(TM) i7-4700MQ CPU @ 
2.40GHz, 16GB RAM, Windows 7 Professional x64, Cygwin 32-bit, mysql Ver 
14.14 Distrib 5.5.41, for CYGWIN (i686) using readline 6.3.

On the other hand I tried to restore the same backup file on linux 
machine (Pentium(R) Dual-Core  CPU E5300  @ 2.60GHz, 4GB RAM, CentOS 
release 6.6 (Final), 32-bit, mysql  Ver 14.14 Distrib 5.1.73, for 
redhat-linux-gnu (i386) using readline 5.1).
Whole database was successfully restored after cca two and half hours of 
run.

Can I tweak something in mysql or cygwin to improve restore (inserts) 
performance?
Any other suggestions, please?

-- 

.: Vlado :.


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