sata raid & write cache state

[Roisin Murphy]

> The main point of write back caching is to give the user faster turnaround
> for their commands without the application having to support deep queueing.

1. that is now taken care of by the 'write back' cache on the raid
controller. So (s)ata raid setups can still perform similarly to scsi
setups. But enough about that :)
anyway, enough of that :)


> Sure, you can recover from a power outage, you just have to scrub the array
> when you come back up.  You also won't know for sure whether you have some
> data corruption.

2. how do you usually 'scrub' the array? is this automatically done by
the controller when it boots up? or does this usually require the user
issuing commands via those raid CLIs?

3. one more thing about the battery back up option, now that i thought
about it, it has to be like a mini PSU that has enough power to keep
all the disks spinning for couple seconds after your main psu/power
dies, so now i understand why it cost $100+