[CentOS] Re: hardware raid vs fake raid

[Tom Diehl]

On Thu, 13 Sep 2007, Ross S. W. Walker wrote:

> 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".

AAH!! That makes sense. I did not think about that but I should have. :-(

>
> 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.

Again, that makes perfect sense. I feel stupid for not figuring it out on
my own. Sometimes one just cannot see the forest for the trees. :-)

Thanks for the education. This list is great!!

Regards,

-- 
Tom Diehl		tdiehl at rogueind.com		Spamtrap address mtd123 at rogueind.com