[CentOS] OT: What's wrong with RAID5

Johnny Hughes johnny at centos.org
Thu Oct 1 02:52:08 UTC 2009


On 09/24/2009 07:35 AM, Rainer Duffner wrote:
> 
> Am 24.09.2009 um 07:43 schrieb Fajar Priyanto:
> 
>> Hi all,
>> Sorry for the OT.
>> I've got an IBM N3300-A10 NAS. It runs Data Ontap 7.2.5.1.
>> The problem is, from the docs it says that it only supports either
>> RAID-DP or RAID4.
>> What I want to achieve is Max Storage Capacity, so I change it from
>> RAID-DP to RAID4, but with RAID4, the maximum disk in a RAID Group
>> decrease from 14 to 7. In the end, either using RAID-DP or RAID4, the
>> capacity is the same.
>>
>> Now, why RAID5 is not supported? I believe using RAID5, I can get more
>> storage capacity, can't I?
>> I also notice with some onboard RAID controller, they only support
>> either RAID0, RAID1, or RAID1+0. No RAID5.
>>
>> What's wrong with RAID5, is there any technical limitation with RAID5?
> 
> 
> 
> Well, it depends on the disk-size:
> http://www.enterprisestorageforum.com/technology/features/article.php/3839636

This info is VERY relevant ... you will almost ALWAYS have a failure on
rebuild with very large RAID 5 arrays.  Since that is a fault in a
second drive, that failure will cause the loss of all the data.  I would
not recommend RAID 5 right now ... it is not worth the risk.



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