Quick question regarding: forums.user... warning : Table is marked as crashed

[john2k]

Been dealing with a server issue lately, or possibly datacenter failing/unstable PDU, which has been causing spontaneous reboots. Has happened a few times so far and I expect to have the source issue corrected very soon.

After the spontaneous reboots, usually the db ends up with '# clients are using or haven't closed the table properly' type issues along with a seemingly unimportant table having crashed (usually humanverify table).

Today, however, the users table reported crashed/corrupt:

forums.user
warning  : Table is marked as crashed
warning  : 2 clients are using or haven't closed the table properly
error    : Checksum for key:  6 doesn't match checksum for records
error    : Corrupt

That was the partial result of the following command: "mysqlcheck -c forums"

After running: "mysqlcheck -r forums" to repair, all seems good:

forums.user                                OK

My question(s):

Is the user table now fine / repaired without any corruption in the text of the database records?

Being that the user table is relatively important, my concerns are that maybe now there could be random user records in that table with messed up information which is not detected as an error by mysqlcheck. Is that possible?

What's the likelihood that this crash/corruption caused further undetected issues?

I'm probably just being paranoid about it, but maybe somebody here who knows more about these things can help me better understand all of this.

Any input / advice is much appreciated.

[Wayne Luke]

Records could be corrupted during a repair. They will no longer be usable. Those users won't be able to login and will need to register a new account. You should perform daily or weekly backups to safeguard your data. Your hosting provider can provide tools to do this.

[john2k]

Records could be corrupted during a repair. They will no longer be usable.

Does that apply only for tables which are crashed/corrupted?

How about tables that were already reporting as "OK"? Would those "OK" tables be potentially corrupted when the repair operation is performed upon the entire database with the following type of command: "mysqlcheck -r database_name" ? Or, would the "OK" tables not be touched by the repair so no risk of potential corruption from the repair?

I'm asking about that because previously I was thinking that "OK" tables were essentially untouched, but now I'm wondering if maybe running 'mysqlcheck -r' could potentially cause issues with tables that have been reporting as 'OK' when the repair operation targets the entire database.

You should perform daily or weekly backups to safeguard your data. Your hosting provider can provide tools to do this.

I have lots of backup files. Perform the backups via Linux shell commands.

Being that you mentioned backups, is it generally preferred to only use 'mysqlcheck -r database_name" repairs as a last resort?

[Wayne Luke]

Only tables marked as crashed can receive corruption. Ideally, you would be using INNODB tables with today's versions of MySQL so the likelihood of having tables that crash is severely diminished.

You should only run repair utilities on the tables that having problems. When using MYISAM and running repairs on healthy tables, you can cause them to fail.