[Novalug] Seagate Momentus XT hybrid Drive

James Ewing Cottrell 3rd JECottrell3@Comcast.NET
Mon May 31 12:43:44 EDT 2010


NetApp notwithstanding, I would be prepared to fight that Religious 
Battle under Any and All Circumstances, especially now that disk is 
Laughably Cheap. But Not Today.

Here I was speaking of ONE special case...Exactly Four Disks...RAID6 vs 
RAID10.

RAID6 is superior in One Small Edge Case...it will survive ANY two disks 
going bad. RAID10 will suvive FOUR out of SIX cases of two going bad.

I like to optimize for the Working Case, not the rare Rare RARE Failure 
case. Now maybe on the Mars Rover...

JIM

P.S. Of course, Dave advice to Optimize the System as a Whole is well 
taken, altho I/O is usually one of the biggest concerns.

On 5/28/2010 4:55 PM, American Dave Kline wrote:
> On Fri, May 28, 2010 at 11:41:24AM -0400, James Ewing Cottrell 3rd wrote:
>
>    
>>     Kudos for the RAID10 format. I recently worked with a groups that used
>>     RAID5 with a spare. Geeze.
>>      
> RAID 5 gets dogged a lot, though in practice it works quite well.  It's
> a good compromise between array size, speed, and reliability.  A hot
> spare as well can buy you a bit more reliability.  As the devices per
> array grows, RAID 5 makes less sense since the chance of having
> concurrent failures grows.
>
> I often see RAID levels get brought into technical religious battles,
> when the time is almost always better spent optimizing the system as a whole.
>
> -A. Dave
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