[CentOS] RAID 5 setup?

Ross Walker rswwalker at gmail.com
Fri Mar 26 14:48:29 UTC 2010


On Mar 25, 2010, at 9:36 PM, Christopher Chan <christopher.chan at bradbury.edu.hk 
 > wrote:

> On Friday, March 26, 2010 09:12 AM, John R Pierce wrote:
>> Christopher Chan wrote:
>>>> but with RAID 10, data is safe after many types of failures.
>>>>
>>>
>>> Except for the case when a mirror dies after which the whole thing  
>>> is
>>> toast but in theory you can survive up to four disks going down.
>>>
>>
>> if you have a 8 drive raid1+0, and a random drive fails, you can  
>> survive
>> any other drive failing *except* the mirror of the failed one.   so  
>> if a
>
> That's what I said right? I did not say when a mirror is broken...
>
>
>> second drive fails, there's only a 1 in 7 chance that its the 'fatal'
>> one.   on a 4 drive raid10, its a 1 in 3 chance.   meanwhile, a  
>> raid10
>> can rebuild from a hotspare in like an hour, if the system isn't  
>> busy,
>> and a few hours in the background if its busy and active.
>
> yeah, I thought the raid10 module would be able to rebuild  
> automatically
> from a hotspare and would therefore be better than using nested  
> raid1+0.
> I better stop the nested raid1+0 thing...does ananconda support the
> raid10 module during install yet? I mean rather, is the raid10 module
> included in the installation initrd yet?

No, not yet, but I always recommend setting up your data arrays  
manually so your intimately familiar with how they are constructed and  
the mdadm command usage is fresh in your head.

Did you know with Neil's raid10 implementation you can store 3 copies  
of the data so ANY two drives can fail before you start playing  
Russian roulette!

-Ross



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