Software RAID 5 or something else?

[Robin Laing]

Alan Cox wrote:
>> So considering that, what do you gain from dedicated hardware for RAID?  
>> You get a commercially supported RAID software and hardware package, and 
>> you get to unload a bit of CPU from the main system.
> 
> The big thing it saves you on in RAID 1 & 5 is memory bandwidth, and in
> RAID5 doubly so for the XOR costs. The second thing it helps with is bus
> bandwidth as each chunk of data crosses the PCI(X) bus once. In the PCI
> world that really helped, PCI-X it's less clear.
> 
> The last benefit is a battery backed cache.
> 
>> Considering that the CPU on the card at max performance is probably 1/3 
>> of a core from a modern CPU, then that is not really much of a savings.
>>
>> The real consideration for RAID 5 is survival.  In either situation you 
>> have to have a spare drive, and you have to consider availability of new 
>> drives to match them in the future.
> 
> Bigger ones will do
> 
> Alan
> 

There is a study that was done on RAID 5 and larger drives and a problem 
has surfaced.

RAID 5 May Be Doomed in 2009
http://www.tomshardware.com/news/RAID-5-Doomed-2009,6525.html

A drive failure could be the end of your data because the array cannot 
be rebuilt due to errors during the rebuild.

Maybe it is a better idea to create a mirror backup procedure.

-- 
Robin Laing