Hi baldfat, I tried to be very careful with that wording. I'm not aware of storage platforms that allow you to embed actions into the I/O path using your own code. If you have examples where I am incorrect, please do share. Thanks!
Isn't that exactly what "every database ever" calls triggers?
From the Postgres docs: http://www.postgresql.org/docs/9.4/static/trigger-definition...
> A trigger is a specification that the database should automatically execute a particular function whenever a certain type of operation is performed. Triggers can be attached to tables, views, and foreign tables.
Even NoSQL DB's like redis or riak have the ability to execute user-supplied Lua resp. Erlang.
http://docs.basho.com/riak/latest/dev/advanced/commit-hooks/
Here are a few scalable open source block/object storage systems:
Lustre
Ceph
tahoe-lafs
XtreemFS
These are all opensource.
For example, if I wanted a fast global-coherent CDN, then all I need are webservers and GPFS, with some glue code to allow auth'd uploads/deletes. geographically scalable, with tiered storage levels.
If you want to run on dodgy hardware, then use XtreemFS. but you'll pay a performance price.
I'd be interested in a comparison in developer language(as in graphs code examples etc.), with a github link or similar.