In this article I write about an alternative way to upgrade a IBM DS4300 SAN system from 73GB fibrechannel to 300GB fibrechannel disks (if you finally were able to get hold of them).

A main objective, besides the added storage capacity, was avoiding downtime of the storage system during the upgrade.
The procedure may sound a bit uncommon and it strongly relies on your confidence to the system and RAID in general, but it worked really smooth.

The upgrade can be done by replacing harddrive by harddrive, each time letting the spare drive jump in and after detecting the new harddrive synchronizing it back. Like many simulated drive failures… I suggest you, to replace only one harddrive per day (takes 14 days in the end).
This procedure avoids downtimes or SAN to SAN copy and only affects the systems performance marginally.
After replacing all harddrives, the system recognizes the added capacity and adds it to the array.