SSDs and their write cache

[omniscence]

With vendors like LSI offering RAID solutions specifically for SSDs like FastPath, the question rises if it makes sense to combine a battery or flash backed RAID controller with an SSD with unreliable write cache. A lot of consumer drives seem to ignore the write cache settings and use it anyway, cutting a hole into the chain between the SSDs flash and the OS. And then there are FUA commands, which should ensure that for SATA drives data really hits the disk on command completion, making a global disable for the write cache obsolete. Does someone know, whether SSDs correctly carry out FUA commands and only indicate completion if the data is on flash storage? If that is not the case, buying a flash or BBU backed RAID controller would be complete nonsense for SSDs.