Raid 1+0

[Brandon J. Wandersee]

Kevin P. Neal writes:

> On Mon, Apr 18, 2016 at 09:07:07PM +0100, Shamim Shahriar wrote:
>> On 18/04/2016 20:22, Bernt Hansson wrote:
>> > Hello list
>> >
>> >
>> > Used gstripe to stripe the arrays raid/r0 + r1 into stripe0
>> >
>> Hi
>> 
>> I'm sure there are people with more expertise than I am, and they can
>> confirm either ways. But in my mind, given that you used RAID1 first
>> (mirror) and then used those two RAID1 to create a RAID0, this is
>> logically RAID 1+0. In other words, if you lose one disc from each of
>> the RAID1 you are still safe. If you lose both from one single mirror
>> array (highly unlikely), the stripe is unlikely to be of any use.
>
> Not that unlikely. If you take identical disks from the same company and
> subject them to identical load then the probability that they will fail
> around the same time is much higher than random.
>
> That's why when I set up a mirror I always build it with drives from
> different companies. And I make it a three way mirror if I can.

Sorry to drag this off-topic, but I've heard this advice more than once
now, and have to ask: when you say "same company," do you mean same
vendor or same manufacturer? I thought having all disks be of the same
make and model was ideal, as it avoids problems arising from the different
ways each manufacturer fudges their total disk capacity. If I'm wrong,
how so? If you mean buying disks of the same make and model from
different vendors is ideal, what's the reasoning there?


-- 

::  Brandon J. Wandersee
::  brandon.wandersee at gmail.com
::  --------------------------------------------------
::  'The best design is as little design as possible.'
::  --- Dieter Rams ----------------------------------