[wp-hackers] Max number of WP sites per MySQL DB

[Andy Skelton]

On Tue, May 11, 2010 at 5:33 PM, Elizabeth Buckwalter
<elizabeth at slatetechpdx.com> wrote:
> I'm interested in knowing at what the physical limitations are to the
> quantity of sites in a single database instance.  I understand that it
> depends on the OS, but I can't seem to find the actual number.  Like
> linux is limited to this number of database tables and windows is
> limited to this number.  Is there a chart or graph anywhere?  It seems
> like this is something that should be in a sys admin "manual"
> somewhere, so others can rtfm.

There is no such thing. Let me give you examples to illustrate why.
The number of files per table depends on the storage engine, e.g.
MyISAM or InnoDB. The number of files per directory depends on the
filesystem, which might have configurable limits. So there are several
factors that determine the maximum number of tables you could create.
But there are other things that limit the number of tables you can
have such as the amount of RAM in the system. Then there are practical
considerations: a server can handle one table getting tons of traffic
or many tables getting virtually no traffic. Some sites are
write-heavy while others are read-heavy, depending on the number
visitors and their aggregate behavior patterns, and the way that
affects your system depends on things like the rotational speed of the
hard drives.

That's just a tiny sample of what a sysadmin has to cope with when a
dataset gets big.

> If 1000 blogs per database is what you guys are doing, then it seems
> that I would have to worry about memory before site limitations.  I
> just don't want to have to scramble if we hit up that limitation
> before expected.

You're going to have to scramble sometimes. Growth a good problem to have.

Andy