RAID

[Dan Nelson]

In the last episode (Mar 11), kalin m said:
> thanks....
[...] 
> 
> in my case the machine showed me the ar0 to install the system on it
> without doing this 'quick and dirty way'.
> 
> and now i get:
> # atacontrol status ar0
> ar0: ATA RAID1 status: READY
> subdisks:
>   0 ad4  ONLINE
>   1 ad6  ONLINE
> 
> that tells me that i actually do have RAID1 active. which means it's a 
> software one, correct?

Right.  The system must have already been set up for RAID when you
bought it.
 
> also if you do not mind please elaborate on "MatrixRAID is one of
> those not-really-raid controllers that only provides RAID during the
> boot process..."

All of the controllers handled by the ataraid device are BIOS-only raid
controllers.  Once the boot process hands control to an operating
system, that OS has to manage the RAID itself, making sure that
mirrored disks are written to, and rebuilding damaged volumes.  This is
different from hardware RAID, where external hardware (usually with a
battery-backed RAM cache to add performance) manages all of that and
the OS just has to read and write blocks to the virtual raid device.

-- 
	Dan Nelson
	dnelson at allantgroup.com