[CentOS] RAID 5 setup?

Ross Walker rswwalker at gmail.com
Sat Mar 27 14:22:00 UTC 2010


On Mar 27, 2010, at 5:07 AM, John R Pierce <pierce at hogranch.com> wrote:

> Robert Spangler wrote:
>> On Thursday 25 March 2010 18:10, Robert Heller wrote:
>>
>>
>>> The prefered way to go would be RAID10 (RAID1 (mirror) + RAID0  
>>> (stripe)).
>>> Form pairs as RAID1, then strip the pairs.  With 8 disks, this  
>>> would 4
>>> pairs, 1.5TB/pair = 1.5*4 = 6TB total.
>>>
>>
>> I am just starting to look into this RAID and I was wondering  
>> wouldn't RAID01
>> be better then RAID10?  In a 4 disc system having the first two using
>> stripping and then backing them up the second set with mirrors?
>>
>> My though is having D1 and D2 as the primary drives stripping and  
>> then having
>> D3 backup D1 and D4 backup D2.
>>
>> And if enough room place a couple more drives in the system as hot  
>> standby's.
>>
>> Or am I looking at this all wrong?
>>
>
>
> for all practical purposes its the same thing.     if it was really
> stripe then mirror, a naive mirror handler would think it would have  
> to
> remirror both drives when one half of one of the stripesets failed and
> was replaced.     but in fact, the mirror handlres tend to be well  
> aware
> of whats going on.      mirror 0+1  aand stripe that with mirrored  
> 2+3,
> and its really all the same    the native raid10 in newer mdraid is
> cleaner because you don't end up with extra partial volume  
> metadevices...

RAID0+1 is never a good configuration because a single drive failure  
in a RAID0 stripe fails out the whole stripe, and with say an 4x2  
RAID0+1, you are more likely to hit a disk failure with 4 drives in a  
RAID0 then 2 in a RAID1.

That's why RAID1+0 came about.

-Ross
  
   


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