Re: Rotating RAID 1

[Pavel Hofman <pavel.hofman@ivitera.com>]

Dne 10.9.2011 00:28, Bill Davidsen napsal(a):
> Pavel Hofman wrote:
>> Dne 16.8.2011 01:55, NeilBrown napsal(a):
>>   
>>>   Also, it doesn't have to be a linear stack.  It could be a binary tree
>>>   though that might take a little more care to construct.
>>>      
>> Since our backup server being a critical resource needs redundancy
>> itself, we are running two degraded RAID1s in parallel, using two
>> internal drives. The two alternating external drives plug into the
>> corresponding bitmap-enabled RAID1.
>>    
> 
> I wonder if you could use a four device raid1 here, two drives
> permanently installed and two being added one at a time to the array.
> That gives you internal redundancy and recent backups as well.

I am not sure you could employ the write-intent bitmap then. And the
bitmap makes the backup considerably faster.

> 
> I'm still a bit puzzled about the idea of rsync being too much CPU
> overhead, but I'll pass on that. The issue I have had with raid1 for a
> backup is that the data isn't always in a logical useful state when you
> do physical backup. Do thing with scripts and hope you always run the
> right one.


I am afraid I do not understand exactly what you mean :-) We have a few
scripts, but only one is started manually, the rest is taken care of
automatically.

Pavel.