Say, I had 4 devices with 500 GB drives exported using iSCSI. If a single larger server took those four iSCSI export drives, and created one md RAID 5 device, could a single server be turned off, and just degrade the array until it was either replaced entirely or brought back online?
how long would it take to replicate and rebuild a volume across the LAN via iscsi? if each of those slices was 500GB, you'd be reading 3 x 500GB and writing 500GB before the drive was resynched. note, a single drive on each storage controller in this scenario won't even achieve 1gigE speeds.