Hello,
I must say I've not still tryed, but with fdisk you can change number of cilinders to set to new size (you must calculate it), and with partprobe (man partprobe) you can reread online "partition table"; now, since kernel gets disk geometry and partition table at boot time, and this command force it to reread almost partition table, I believe (hope) that reread entre disk geometry.
I will try in a couple of month, for now I've changed array size of many HP Proliant but always with reboot.
I suggest you to search about partprobe command features.
Stefano
We just had our servers fitted with more disks. Most of the disks are growing existing RAID 1+0 channels, some are in new channels. Controllers and disks support live installation.
I'd like to avoid a reboot just to let the system find that the disks are larger.