IBM i Storage Sizing Buyer's Guide

Pull real performance data before comparing hardware

Storage sizing conversations that start with free space remaining often miss the actual problem. Buyers should pull current ASP disk busy percentage and I/O wait trends first, since these numbers reveal whether the environment is genuinely storage constrained or facing a different bottleneck entirely.

That data also shapes how much headroom the next storage purchase should include, rather than sizing purely for today's data volume.

Choose between internal expansion and external SAN attachment

Internal DASD expansion is the simpler path when the goal is more disk pool capacity on a single server. External SAN attachment makes more sense when a business wants to consolidate IBM i storage management with other platforms already using shared SAN infrastructure.

SAN attachment adds real implementation complexity, including host adapter compatibility and multipathing configuration, so it should be chosen for a genuine consolidation goal rather than because it seems like the more modern option.

• Internal DASD expansion: simpler, lower implementation complexity
• External SAN attachment: supports storage consolidation across platforms
• Both require confirming adapter and firmware compatibility first

Confirm compatibility before hardware ships

Storage adapter and drive compatibility on IBM Power hardware is generation-specific. Buyers should confirm compatibility with the exact server model and current firmware level before finalizing an order, rather than assuming general storage hardware will work without verification.