Re: [PATCH RFC] btrfs: implement a new compat RO feature, data_io_size

在 2026/7/31 21:10, Sun YangKai 写道:
> On 2026/7/22 18:03, Qu Wenruo wrote:
>>
>> Full stripe 16K, then the new RAID5F chunks will require power-of-2
>> disks, and no more than 16K/4K disks.
>>
>> So no 4 disks RAID5F chunk in the first place.
> 
> I've got your idea and got the following 2 concerns:
> 
> 1. the device count is limited to 3 or 5 device for RAID5, and 4 or 6
> devices for RAID6, losing the flexibility currently btrfs have;

Why you think 16K is the only block size?

You can go as large as 64K, which means 16 data devices which is more 
than enough for common usages.

In fact, I do not think you should have overly flex design, which is 
contributing to the write-hole in the first place.

> 
> 2. On each device, we will send a lot of 4KiB or 8KiB io, which might be
> not good for performance;

It can always be solved usings blk plugs.

> 
> So I personally don't think this is a good way to fix the write hole issue.

I do not think so.

As I have already said, at least I know XFS is planning doing something 
similar. Although not to solve write-hole.