MySQL growth 500k records/day Im not a DBA however am an infrastructure guy used to installing and configuring database servers such as MSSQL, MySQL, MongoDB etc...

I have a MySQL database which is being used for archival of building systems data. Once a night, the building management system will archive its data which results in around 500k rows of data being added across various tables in the database. 

There are 12,000 tables in this database and overall it contains 7 billion records. 

Are there any issues with growth? The database is currently 150GB and this is a purely write only load. There will hardly ever be any read activity on this DB.

I understand IOPS and performance scaling, this is a question about MySQL itself and specifically its ability dealing with a DB of this size.

Is there anything I should be aware of?

EDIT: I am fully aware that this is not ideal, hence this post but I am totally 100% unable to change the way the third party stores its info in the DB so don't have much of a choice but ask how I can best 'optimise' SQL to work with what its given.

Thanks
MySQL can handle it, but not without some care.

12,000 tables is a red flag.  Each table is one (or more) OS file.  This large a number, especially if in a single database, can cause sluggishness.

Are the records merely written to the tables?  Or are they used to "update" existing rows?

I would load the 500K rows into a table(s), cleanup the data, then copy it into the real tables.

Generally, I would do the work 1000 rows at a time.  But this might vary depending on whether you have Replication, which Engine you are using, etc.

7B in 150GB smells like MyISAM; is it?

If you are "never" reading it, why put it in a database?  Why not in flat files?

What does the incoming data look like?  CSV?  mysqldump?  Other?

Simple-minded code should be able to load a nightly dump in an hour or two.  More advanced coding might get it down to less than an hour.