Sadly Number of physical boxes is usually not the issue with resource
bottle neck; it is that you are always running close to capacity and
can not convince anyone to purchase more equipment because things are
running fine. Double the number of fsyncs on a box and then you get a
complaint that everything runs too slow and it must have been
something you did so undo it :(
With checksum - I am more then willing to admit I have not done any
production MySQL work in a while but I remember that it could be done
live. Also indicated in the manual.
------------------------------------------------------------------------------------------------------
12.4.2.4. CHECKSUM TABLE Syntax
CHECKSUM TABLE tbl_name [, tbl_name] ... [ QUICK | EXTENDED ]
CHECKSUM TABLE reports a table checksum.
With QUICK, the live table checksum is reported if it is available, or
NULL otherwise. This is very fast. A live checksum is enabled by
specifying the CHECKSUM=1 table option when you create the table;
currently, this is supported only for MyISAM tables. See Section
12.1.10, “CREATE TABLE Syntax”.
With EXTENDED, the entire table is read row by row and the checksum is
calculated. This can be very slow for large tables.
If neither QUICK nor EXTENDED is specified, MySQL returns a live
checksum if the table storage engine supports it and scans the table
otherwise.
For a nonexistent table, CHECKSUM TABLE returns NULL and, as of MySQL
5.0.3, generates a warning.
The checksum value depends on the table row format. If the row format
changes, the checksum also changes. For example, the storage format
for VARCHAR changed between MySQL 4.1 and 5.0, so if a 4.1 table is
upgraded to MySQL 5.0, the checksum value may change.
On Sat, Jul 24, 2010 at 10:53 AM, Alex Dean <
alex@crackpot.org> wrote:
>
> On Jul 24, 2010, at 12:47 PM, Bryan O'Neal wrote:
>
>> I agree with Alex but this just follows logical design of separation.
>> You dev, qa, prod, ha, and dr environments should be separated and
>> used for those set purposes. Unfortunately I also know that if this
>> most elementary step has not been take it is usually due to a lack of
>> required resources not simple oversight. But even if you do that
>> should not replace the monitoring scripts or, as you mentioned, the
>> commitment to repeatable and documented automated operations.
>
> Not a big deal to run multiple instances of MySQL on different ports on the
> slave machine. Search for mysqld_multi.
>
>>
>> BTW Alex if all you want to do is verify you are in sync you can do a
>> checksum on the tables in both servers. If they are in sync the
>> checksums will match - again, great automated monitoring check.
>
> You can do that if mysql is stopped.
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