Re: possibly silly question (raid failover)

[Jonathan Tripathy <jonnyt@abpni.co.uk>]

On 02/11/2011 07:02, keld@keldix.com wrote:
> On Wed, Nov 02, 2011 at 12:48:16PM +1100, NeilBrown wrote:
>> On Wed, 2 Nov 2011 02:37:56 +0100 keld@keldix.com wrote:
>>
>>> On Wed, Nov 02, 2011 at 09:25:26AM +1100, NeilBrown wrote:
>>>> On Tue, 1 Nov 2011 23:15:39 +0100 keld@keldix.com wrote:
>>>>
>>>>> On Tue, Nov 01, 2011 at 04:13:26PM -0400, Miles Fidelman wrote:
>>>>>> David Brown wrote:
>>>>>>> No, md RAID10 does /not/ offer more redundancy than RAID1.  You are
>>>>>>> right that md RAID10 offers more than RAID1 (or traditional RAID0 over
>>>>>>> RAID1 sets) - but it is a convenience and performance benefit, not a
>>>>>>> redundancy benefit.  In particular, it lets you build RAID10 from any
>>>>>>> number of disks, not just two.  And it lets you stripe over all disks,
>>>>>>> improving performance for some loads (though not /all/ loads - if you
>>>>>>> have lots of concurrent small reads, you may be faster using plain
>>>>>>> RAID1).
>>>>> In fact raid10 mas a bit less redundancy than raid1+0.
>>>>> It is as far as I know built as raid0+1 with a disk layout
>>>>> where you can only loose eg 1 out of 4 disks, while raid1+0
>>>>> in some cases can loose 2 disks out of 4.
>>>> With md/raid10 you can in some case lose 2 out of 4 disks and survive, just
>>>> like raid1+0.
>>> OK, in which cases, and when is this not the case?
>>>
>>> best regards
>>> keld
>> "just like raid1+0"
> No, that is not the case AFAIK. Eg the layout of raid10,f2 with 4 disks is
> "just like raid0+1".
>
Isn't md raid10 n2 exactly the same as RAID1+0??