Comment 12 for bug 320638

@Stephan, As I understand this, you are using an md raid1 to save power and have a "backup"? This is failure prone and dangerous to your data. The MD layer is pretty resilient but it is meant for RAID of like disks. This is why the numbers are weird. It "expects" a scsi/sata hdd and works best if they are matched, i.e. same disk model. Mixing in a usb stick is not the same thing. You save little, if any, power because an array restore requires a complete disk copy, not an update of some number of out-of-date blocks. I wouldn't be surprised if it consumes even more since it is a steady state transfer load until the restore is complete. This restore, depending on subsystem traffic and disk size can take a significant amount of time. It can also leave your system vulnerable. I have heard of reiser filesystems fail w/ compromised raid arrays, which this is in your powersaving mode. There is power management in the newer kernels to cycle down the hdd to conserve power but this takes careful tuning. If you want backup with this mix of devices, use rsync to the usb stick. This will be consistent and only write what is needed. A usb stick is not the same as an SSD. The former is meant as a replacement for floppies, namely lower than hdd transaction rates, removability, and expected limits to lifetime. The later is meant for hdd type applications. I suggest you reconsider your configuration.

I did not "invalid" this bug yet pending your reply.