We use 3ware Inc 9650SE SATA-II RAID PCIe RAID controllers with battery backed write cache. Our spare hardware has the same controller.

I was wondering; are these controllers smart enough not to sync the cache when the disks have been changed? For example, if I deploy one of those spare machines by putting in the disks of another machine and that spare machine still has pending writes, will it be smart enough not to perform those writes on the replaced array?

Edit: my scenario is not really made clear, so let me give an example:

1. server1 goes down because of power supply failure.
2. I put the disks in server2 and start.
3. I repair server1
4. I put the disks back from server2 in server1 (it's not relevant right now that in reality I would probably keep server2 running).
5. If server1 doesn't have safeguards, it will write to the array, thinking it's simply powering up again, corrupting it.