this is the storage information I was able to put together out of there catalog tables.  They don't have much...

SELECT * FROM informix.syschunks c LEFT JOIN informix.sysdbspaces s ON c.chknum = s.dbsnum LEFT JOIN informix.syschkio i ON c.chknum = i.chunknum
go
select * from sysextspaces
go
select * from syslogs


//The syschunks table describes each of the chunks that the database server manages
select * from informix.syschunks
go
//The sysdbspaces table describes each of the dbspaces that the database server manages.
select * from informix.sysdbspaces
go
// The syschkio table provides I/O statistics for individual chunks that the database server manages.
select * from syschkio
go
//The sysextspaces table provides information about external spaces. Indexes for the id column and the name column allow only unique values.
select * from sysextspaces
go
//The syslogs table provides information about space use in logical-log files.
select * from syslogs

Some more info here:
http://publib.boulder.ibm.com/infocenter/idshelp/v111/index.jsp?topic=/com.ibm.sqls.doc/sqls1290.htm

and there: http://www.openadmintool.org/