[CentOS] /dev/sd and /dev/mapper

Fri Jun 24 15:23:50 UTC 2011
Ljubomir Ljubojevic <office at plnet.rs>

Alexander Dalloz wrote:
> Am 24.06.2011 14:24, schrieb Steve Campbell:
>> I've done a little research, and can't really find out why it happens, 
>> but on one server I have built, I get the old fashion /dev/sda1, 
>> /dev/sda2 type partitions and on another server I get the /dev/mapper 
>> style partitions. Both machines are hardware raided (before the install) 
>> and both machines are Centos 5.5 64 bit, using the same set of CDs to 
>> install from.
>>
>> Can someone please explain why this happens? I'm not sure it matters, so 
>> this is just a curious bother. The machines are different brands with 
>> different raid controllers. Both were partitoned using the "custom 
>> layout" when installed. I'm thinking I must have overlooked a checkbox 
>> or something during the install.
>>
>> This is not a big deal, not a problem, it's just an itch in my brain.
>>
>> Thanks for any explanation.
>>
>> steve campbell
> 
> The machine with the /dev/sda has a true hardware RAID controller. The
> machine with a /dev/mapper device has just a fake RAID controller, thus
> a dm-raid device.
> 
> Alexander

Instead of fake-raid controller, I suggest software RAID via mdadm 
(Linux md).

Ljubomir