Neil Zanella wrote:
>
> Sorry about this questions but why would you want to run two copies of
> mysqld when it is capable of hosting as many different databases as
> you need? Even if you needed two databases with the same name you
> could still just create two different MySQL users for it.
>
> Thanks,
>
Hi,
I see several reasons for that:
- mysqld is a multithreaded single process. That meens it cannot use
more than 4Gb of RAM on 32 bits OS (and if fact much less, 2G to 3.5Gb
depending on OS configuration). Since you can have highend Intel
servers with more than 4Gb of RAM, you will make much better use
of your RAM with multiple mysqld instances.
- If you want to have a very high number of simultaneous connections,
you must have several mysqld running. For instance, mysqld on Linux is
limited to ~1500 simultaneous connections; if you want more, you have
to use several mysqld. (Of course, you can do that only if all your
clients don't use the same database).
- Minimising MySQL downtime: Each time one mysqld process crashes, you
just have to repair the databases it was managing. For instance, if
you have 4 databases served by 4 mysqld, you just repair one database
instead of 4 before restarting. (Please no flames here, I know that
MySQL is considered as very stable; however, it sometimes crashes:
there were several reports of "mysqld killed by signal 11" on this list)
Of course, most MySQL users don't need to run more than one mysqld, but you
asked, so here are some reasons.
Regards
--
Joseph Bueno
NetClub/Trader.com
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