what raid controller?

[Eberhard Roloff]

Jonas Norlander wrote:
> 2008/9/22 John DeCarlo <johndecarlo at gmail.com>:
>> On Sun, Sep 21, 2008 at 3:51 PM, uriah heep <stan10x10 at gmail.com> wrote:
>>> I would like to set up mirroring on 2 sata WD hard drives.  Could any one
>>> suggest a good low cost controller.  This is for a home computer not
>>> business.
>> I agree with those who say that software RAID is the way to go.  Much safer,
>> more reliable, cheaper
>>
> 
> I don't agree with you that a software RAID should be safer and more
> reliable than a real hardware RAID, it's one more layer that can mess
> things up if your are unlucky, but it's much cheaper and that could
> make it worth it depending how value your data is.

If your data has any value, you better have a good backup. Linux 
Software Raid is a proven, very good alternative, and according to 
measurements from my favourite PC magazine (ct in germany) it almost 
always works at marginally the same speed as real hardware raid, as long 
as your CPU is not strangled by other heavy loads.

In contrast, software raid has its advantage, when you come to change 
hardware. Should your motherboard or hardware controller go south, you 
will not succeed without a replacement unit. With software raid, you 
simply install the same raid on the new computer and on you go.

> 
> / Jonas
> 

I would like to add to it now that I learned a few things.
While Linux supports a lot of "fake raid" chipsets, it does so by using 
dmraid without any special "drivers" for the chipset on which it runs.

At first, this may look like a disadvantage against windows, where any 
mobo manufacturer has its own driver disk. But it is in fact a huge 
advantage.

When a windows fake raid dies and you cannot get the same motherboard or 
at least a mobo with a compatible fake raid, you will NOT have any 
access to your data anymore.

This is true, except for Linux dmraid. As long as the original chipset 
was supported by dmraid (not any chipset is supported!) you can use 
dmraid to rebuild the raid in software even on a machine that has no 
"hardware" raid capabilities at all.
Thus, dmraid opens up your disks for data access, again.

So you "only" lost your data, if dmraid does not support your original 
setup.

Not bad for a software solution, I think.

Kind regards
Eberhard