[clug] Hardware Assisted RAID (RAID through BIOS/Chipset RAID)

Tomasz Ciolek tmc at vandradlabs.com.au
Wed Oct 10 15:18:06 MDT 2012

Hi All
I am going to join the discussion, as this (storage) is something that of some 
interests to me...  I also think there is a larger issue to discuss here - and
 that one of dedicated fucntions and general purpose devices.

I think what Martjin is driving at, and I have to agree with him, is that a 
dedicated hardware piece of hardware (raid controller) specifially designed to 
do a certain task, coupled with high quality dedicated software (frimware) is 
the way to go if your goal is to reliably and concistently aggregate and serve 
large volue of data.

On Wed, Oct 10, 2012 at 09:04:40PM +0200, Martijn van Oosterhout wrote:
> But hardware RAID can have advantages, for example Battery Backup on
> your RAID card with onboard RAM will do wonders for your fsync rate,
> which will make your RDBMS very very happy. They can have external
> connectors which let you attach 30+ HDDs on a single controller.

That however is true of any dedicated system that is used for the task it 
was specifically  designed to do. This is because as part of the desing process
a umber of ptimisations are built into the product to make it better at that one thing it will do (RAID, network, etc)

My personal experience is that:

* BIOS RAID is often no better than the software RAID layer in Linux, and it
is much harder to patch, should someone disocver a bug. This is the fleximbility
of a general purpose system - it can do it, but its not greatest at it.

* A dedicated raid controller card on the other hand, canmake a huge difference
to system performace, especially when you need to manage a RAID volume(s) that
span many disks. The disadvantage is the cost of the hardware.

In my mind this comes down to a (not so simple) question - is the expenditure 
on a  dedicated fucntion device such as a raid controller needed for my system
performance and can it be jsutified innterm sof return on investment.

Now that I have middued the waters and ranted for a bit, its time to go and do
the $DAYJOB thing


Tomasz M. Ciolek	
 tmc at vandradlabs dot com dot au 
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