[CentOS] looking for RAID 1+0 setup instructions?

Ross Walker rswwalker at gmail.com
Mon Aug 31 17:51:27 UTC 2009

On Aug 30, 2009, at 10:33 PM, Christopher Chan <christopher.chan at bradbury.edu.hk 
 > wrote:

>>>> How would one setup RAID 1+0 (i.e. 2x mirror'ed RAID1's and then a
>>>> RAID 0 on top of it) on say CentOS 4.6 ?
>>> Setup both RAID-1 arrays then stripe them with LVM?
>>> http://www.redhat.com/magazine/009jul05/features/lvm2/
>>> Though I'd prefer to opt for a hardware raid card, I think
>>> you said you had SATA disks, which if that's the case would
>>> go for a 3ware.
>>> nate
>>> _______________________________________________
>> Nate, this is what I was looking for  :)
>> I'm going away for 2 weeks now, but will definitely give it a shot as
>> soon as I can,
> I would NOT do that. You should like the md layer handle all things  
> raid
> and let lvm do just volume management.

Your under the asumption that they are two different systems.

Md RAID and LVM are both interfaces to the device mapper system which  
handles the LBA translation, duplication and parity calculation.

I have said it before, but I'll say it again, how much I wish md RAID  
and LVM would merge to provide a single interface for creation of  
volume groups that support different RAID levels.

> To create a raid1+0 array, you first create the mirrors and then you
> create a striped array that consists of the mirror devices. There is
> another raid10 module that does its own thing with regards to  
> 'raid10',
> is not supported by the installer and does not necessarily behave like
> raid1+0.

Problem is the install program doesn't support setting up RAID10 or  
layered MD devices.

I would definitely avoid layered MD devices as it's more complicated  
to resolve disk failures.

In my tests an LVM striped across two RAID1 devices gave the exact  
same performance as a RAID10, but it gave the added benefit of  
creating LVs with varying stripe segment sizes which is great for  
varying workloads.


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