[mythtv-users] OT Hardware RAID 5 Recommendations

Yan Seiner yan at seiner.com
Tue Dec 12 19:40:57 UTC 2006

Brian Wood wrote:
> On Dec 12, 2006, at 12:15 PM, Yan Seiner wrote:
>> I've been doing software RAID5 for years.
>> There's nothing to it; it barely loads up the CPU, even on  
>> underpowered
>> boxes.
>> If you need to sync a new drive, that will take a while, but otherwise
>> in operation it is transparent.
> Hmmm... I haven't seen actual numbers but calculating the parity info  
> does require *some* CPU.    The last time I compared them, systems  
> with H/W RAID5 were significantly faster than ones using S/W RAID,  
> but that was back when a 400Mhz. CPU was "fast".

On my old server  - SMP 1GHz PIII - the raid processes never got above 
5% CPU.  On my new server - a 2.13 GHz Intel Core2 - the raid processes 
don't even make it into the top display, so their usage must be 
practically 0%.

> One big advantage to software RAID is that the drives can be used on  
> any Linux system without needing specific hardware, where hardware  
> RAID depends on a specific card type being available. If a card type  
> is discontinued you could potentially be in trouble, while with a S/W  
> RAID system you should always be able to get your info in the event  
> of H/W failure.

Yup.  Also, the controllers are notoriously fickle; it's a crap shoot if 
a particular drive will work or not.

A bit more CPU is cheaper than a RAID controller any day.


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