I am sure this is really simple. I have a setup of 2 disks (sda, sdb) which are outwardly identical, and are mirrors of each other. Together they form 3 raid1 devices. Both disks can boot. Now sda has bad sectors, and I should replace it. But which one of the physical disks is sda?? The machine boots fine from either one of the disks, (and the booting disk of course is always called sda). In the messages log I see entries like this: Apr 29 02:21:07 a134-224 kernel: ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300) By noticing which SATA link (ata1, ata2) is up and which is down, I can find out which physical disk is connected to ata1 and which to ata2. If both disks are connected, will the hd in ata1 become sda, and the hd in ata2 become sdb?? - Jussi