what raid controller?

[Emanoil Kotsev]

--- On Sun, 10/12/08, Eberhard Roloff <tuxebi at gmx.de> wrote:

> From: Eberhard Roloff <tuxebi at gmx.de>
> Subject: Re: what raid controller?
> To: kubuntu-users at lists.ubuntu.com
> Date: Sunday, October 12, 2008, 4:18 PM
> 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.
> 

I've been admistrating few companies with more than 200 employes and using software raid was the best choice.
I'm using it also at home and this year I've been testing software raid on external usb boxes.
The great advantage of linxu software raid over hardware one is also that mdadm utility do monitor your devices and if one fails you first get e-mail and second can easlily replace it.
Having a hardware raid you should look all the time at the leds if they light green, yellow or red.
The overhead by the raid layer is minimal and raid has been tested extensively so it's kind of production software but I always tend to say - use it at your own risk htough ;-)

regards