Re: btrfs RAID5 or btrfs on md RAID5?

[Mark Harmstone <mark@harmstone.com>]

On 21/10/2025 4.53 pm, Christoph Anton Mitterer wrote:
> On Tue, 2025-10-21 at 16:46 +0100, Mark Harmstone wrote:
>> The brutal truth is probably that RAID5/6 is an idea whose time has
>> passed.
>> Storage is cheap enough that it doesn't warrant the added latency,
>> CPU time,
>> and complexity.
> 
> That doesn't seem to be generally the case. We have e.g. large storage
> servers with 24x 22 TB HDDs.
> 
> RAID6 is plenty enough redundancy for these, loosing 2 HDDs.
> RAID1 would loose half.
> 
> 
> Cheers,
> Chris.
So for every sector you want to write, you actually need to write three
and read 21. That seems a very quick way to wear out all those disks.
And then one starts operating more slowly, which slows down every write...

I'd still use RAID1 in this case.