Problem with sata2 and raid1.

[Erik P. Olsen]

On 14/04/08 15:13, Peter Boy wrote:
> Am Samstag, den 12.04.2008, 15:42 +0200 schrieb Erik P. Olsen:
>> I have installed two sata 2 drives - each 250 GB - which I want to use in a 
>> raid1 configuration. My mobo - MSI K8T Neo2 - does not support those sata 
>> drives, so I have therefore installed a RocketRaid 1720 PCI-card to get the 
>> necessary hardware support.
> 
> As to my knowledge the 1720 is not a real hardware raid controller but a
> fake raid, i.e. the controllers firmware provides some software to do
> some limited raid management, but all the real work is done by your
> computers hardware via kernel drivers.
> 
>> I have therefore decided to switch to the software available with Fedora and 
>> would like to know if the data already located on the disks is accessible to the 
>> Fedora driver or if I have to reformat the drives and install all the enchilada 
>> from the beginning? 
> 
> There is a chance that both use a standard format to manage the raid
> disks, so your data may be readable. If you have a full backup you
> should just try.
> 
>> Luckily I have back-up of everything and can recreate all 
>> data it just takes more time. Another even more important question is will 
>> Fedora drive the disks through the RocketRaid controller or should I get 
>> different hardware and if so which?
> 
> In both cases you drive the disks through the 1720. If you use dmraid,
> the controllers bios is used for some operations. I you use md, you
> disable the controllers bias and just use the SATA connectors and drive
> access logik. 
> 
> In terms of performance: it's equal. read is the same as if you had a
> single disk, write doubles the time needed to write to the disks
> (because write operations will be performened twice, one operation for
> each disk).
> 
> In terms of administration: md does not use propriarity firmware
> drivers. In case of a failure or other problem it is easier to check and
> handle the disks.

I know next to nothing about md and dmraid. Is there a howto doc somewhere that 
I could read?

-- 
Erik.