maria-discuss team mailing list archive

[<Rhys.Campbell@xxxxxxxxxxxx>]

This doesn't touch the mysql db. They would still be myisam. You have to explicitly do an ALTER to innodb I think.

From: Roberto Spadim [mailto:roberto@xxxxxxxxxxxxx]
Sent: 06 June 2018 16:21
To: Campbell Rhys, INI-ONE-SCC-MVS-IMQ <Rhys.Campbell@xxxxxxxxxxxx>
Cc: jm@xxxxxxxxxx; Maria Discuss <maria-discuss@xxxxxxxxxxxxxxxxxxx>; seb@xxxxxxxxxx
Subject: Re: [Maria-discuss] Why MyISAM as default engine for system tables ?

Last time i had a innodb problem i changed all innodb to one file per table

2018-06-06 9:11 GMT-03:00 <Rhys.Campbell@xxxxxxxxxxxx<mailto:Rhys.Campbell@xxxxxxxxxxxx>>:
"why keep using MyISAM as default engine for system tables, when MariaDB has Aria or InnoDB ?"

Probably because of the time required to implement and test this. To be honest you were probably just very unlucky. Generally the MySQL db receives few writes so the chances of corruption are very small. I can honestly say I've never had this issue in over 10 years of working with MySQL/MariaDB.

As I recall the documentation does warn you not to change the mysql table to another other engine. Has anyone else tried?

Rhys

-----Original Message-----
From: Maria-discuss [mailto:maria-discuss-bounces+rhys.campbell<mailto:maria-discuss-bounces%2Brhys.campbell>=swisscom.com@xxxxxxxxxxxxxxxxxxx<mailto:swisscom.com@xxxxxxxxxxxxxxxxxxx>] On Behalf Of Julien Muchembled
Sent: 06 June 2018 12:38
To: Maria Discuss <maria-discuss@xxxxxxxxxxxxxxxxxxx<mailto:maria-discuss@xxxxxxxxxxxxxxxxxxx>>
Cc: Robin Sébastien <seb@xxxxxxxxxx<mailto:seb@xxxxxxxxxx>>
Subject: [Maria-discuss] Why MyISAM as default engine for system tables ?

Hello,

A few weeks ago, we got the following fatal error when starting mariadb:

[Note] Starting crash recovery...
[Note] Crash recovery finished.
[ERROR] mysqld: Table './mysql/db' is marked as crashed and should be repaired
[Warning] Checking table:   './mysql/db'
[ERROR] mysql.db: 1 client is using or hasn't closed the table properly tch value count at row 1 [ERROR] Aborting

Unfortunately, what led to this is unclear. We only rebooted the machine. Maybe a hw raid issue. We did a copy at that time. I tried recently if it could be repaired but I don't have the a fatal error anymore. We also don't know why system tables were touched during the reboot.

Anyway, given the description of Aria ("Crash-safe tables with MyISAM heritage"), I understand that MyISAM is not crash-safe. Then, why keep using MyISAM as default engine for system tables, when MariaDB has Aria or InnoDB ?

Not sure a crash-safe engine would have helped in the above case (there's no miracle for data corruption). But we'd like at least that all our mariadb setups are crash-safe (e.g. power cuts) and we use InnoDB partly for that. And I don't know if a InnoDB DB could be always recoverable if the 'mysql' DB is lost but we don't want to do manually (and learn how to) what the machine can do automatically.

Julien

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--
Roberto Spadim
SPAEmpresarial - Software ERP
Eng. Automação e Controle