I'm planning to store gigantic arrays into serialized files and read from them in order to display data within them. The idea is to have a simple, document-oriented, filesystem database. Can anyone tell me if this would be a performance issue? Is it going to be slow or very fast?
Is it worth, filesystem is always really faster?
It will be very slow. Serializing and unserializing always requires reading and processing the whole array, even if you need only a small part.
Thus you are better of with using a database (like MySQL). Or if you need to only access key/value use APC/memcached.
You'll be much better off using a "proper" database - it's what they're designed for. If your data is really in a document-oriented format, consider CouchDB.
I think you could implement this without many performance issues, just so long as your arrays don't take forever to (un)serialize and you are able to lookup your files efficiently. How do you plan on looking up which file to read, btw?
Is it worth, filesystem is always really faster?
No, this method is not always faster, in fact you'd probably get better performance using some sort of db or cache with what you're trying to do.
Quite big, a multidimensional array with +- 5,000 entries.