[CentOS] Re: hardware raid vs fake raid

Ross S. W. Walker rwalker at medallion.com
Thu Sep 13 15:57:36 UTC 2007

Tom Diehl wrote:
> On Thu, 13 Sep 2007, Ross S. W. Walker wrote:
> > Tom Diehl wrote:
> >>
> >> Hi Tim,
> >>
> >>
> >> On Thu, 13 Sep 2007, Tim Verhoeven wrote:
> >>
> >>> On 9/13/07, Tom Diehl <tdiehl at rogueind.com> wrote:
> >>>>
> >>>> Does anyone know how  I can find out if an ibm serveraid
> >> 8k sas storage
> >>>> controller (zero channel RAID) is a real hardware RAID
> >> controller and
> >>>> supported in the standard CentOs kernel or is it a fake
> >> raid controller.
> >>>> I am trying to decide if I should get the serveraid
> >> controller or go get
> >>>> a 3ware controller.
> >>>
> >>> Tom,
> >>>
> >>> The ServeRAID 8k s a real hardware raid controller, is 
> has 256 MB of
> >>> cache I think and a battery backup. So in this case there 
> is no need
> >>> for a 3ware controller. On the IBM website you can also find a
> >>> commandline tool (called arcconf) that allows you monitor and
> >>> configure the controller inside Linux.
> >>
> >> Is there a place where this kind of thing is documented? I
> >> looked through Google
> >> for about 3 hrs yesterday and I could not find anything definitive.
> >>
> >> Thank You, for the info.
> >
> > I hate to be the stater of the obvious... but doesn't IBM's website
> > provide product specs along with a compatibility guide?
> They do but nothing I can find in there tells me if it is 
> real hardware
> raid or fake raid.  Adaptec for example, also says that their 
> fake raid cards
> are comaptable with Linux but they do not clearly specify if 
> it is fake raid
> or true hardware Raid. AFAIK the Adaptec cards are all fake 
> Raid. and some of
> ServeRaid cards were also based on the Adaptec chipset and 
> hence Fake Raid.
> When I looked at the IBM specs for the ServerRaid cards I did 
> not see anything
> that indicated if the were real hardware raid or Fake Raid. 
> If I am missing
> something please enlighten me. I am always willing to learn.
> IMO this type of thing is ambigious at best.

Ok, if a card has an IO processor then it will definitely be a
true RAID card, as the fake ones don't have IO processors and
use the system processor as it's processor and thus why they
are "fake".

So look for a mention of an Intel/LSI/Broadcom on-board processor
in the specs and take note of the IO processor model # as that
will determine it's performance.


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