Ask the following interrelated questions to determine what storage devices you need. For example, the speed and type of storage devices partly determine the number of storage devices that you need.
The transaction volume and the size of your database are major factors in determining the kind of storage devices that you need.
ISM supports simple tape devices such as QIC, 4mm, 8mm, DLT, optical devices, and disk backups. If ISM cannot manage the storage devices that you need, you need to purchase a different storage manager. For more information, see the IBM Informix: Storage Manager Administrator's Guide.
Is it important for your storage devices to allow random as well as sequential access? If so, you cannot use tape storage devices.
ISM supports up to four devices per host. The number of storage devices that you need depends on the kind of storage devices you have, how much transaction activity occurs on the database server, how fast throughput is, how much time you can allow for backups, and other similar factors.
You can have one storage manager on each coserver node.