Re: RAID1 vs RAID10

[Andrei Borzenkov <arvidjaar@gmail.com>]

08.11.2025 05:10, Nicholas D Steeves wrote:
> Andrei Borzenkov <arvidjaar@gmail.com> writes:
> 
>> On Mon, Oct 20, 2025 at 3:23 PM Ulli Horlacher
>> <framstag@rus.uni-stuttgart.de> wrote:
>>>
>>>
>>> I have just discovered, that RAID1 is possible with more than 2 devices:
>>>
>>> https://btrfs.readthedocs.io/en/latest/mkfs.btrfs.html#profiles
>>>
>>> What is the difference to RAID10?
>>>
>>
>> In RAID1 each chunk (copy) is located on a single disk. In RAID10 each
>> chunk (copy) is striped across multiple disks.
>>
>> https://lore.kernel.org/linux-btrfs/87v8qokryt.fsf@vps.thesusis.net/T/
> 
> Does the RAID10 profile still have equivalent read-speed to RAID1
> profile on recent (>=6.12) kernels?  Last I looked into it both were
> still limited to the speed of a single-device.
> 

This is true for any single stream IO pattern unless it is using very 
large blocks.

To parallelize the single stream IO the stripe width (stripe element 
size, strip size) needs to be small enough. OTOH it will kill sequential 
IO.