[CentOS] Generic RAID question

[Ross Walker]

On May 19, 2010, at 1:59 PM, Benjamin Franz <jfranz at freerun.com> wrote:

> On 05/19/2010 10:50 AM, James Bensley wrote:
>> Does anyone know if using unequal drives in a RAID 0 is possible?
>>
>> I was looking to set up a software stripe but if I have two volumes  
>> of
>> unequal size I wish to stripe over, will the OS try and work around
>> this by say only using as much space as is available on the smallest
>> drive or is there anyway it will use all of both drives?
>>
>> Does it have to be a perfect block/byte balance across drives? (I'm
>> assuming yes?)
>>
>>
> In general, RAID0 will only size to the smallest volume. If your  
> goal is
> just to make the largest volume out of multiple smaller volumes, use  
> LVM
> instead. If you specifically want the performance enhancement of  
> RAID0's
> striping you will have to live with it sizing to the smallest drive.

Actually using LVM you can do both!

If you create the LV over two PVs, one bigger then the other, provide  
a size greater then the smaller can fit (size/2 > smaller disk free  
space) with an interleave of 2 it will put the remaining allocations  
sequentially on the bigger drive. Of course not ideal, but possible.

-Ross