Re: Avoiding BRTFS RAID5 write hole

Hubert Tonneau
2019-11-12T21:27:05Z

Goffredo Baroncelli wrote:
>
> Instead I would like to investigate the idea of COW-ing the stripe: instead of updating the stripe on place, why not write the new stripe in another place and then update the data extent to point to the new data ? Of course would work only for the data and not for the metadata.

We are saying the same.
What I am suggesting is to write it as RAID1 instead of RAID5, so that if it's changed a lot of times, you pay only once.

The background process would then turn it back to RAID5 at a later point.
Adjusting how aggressively this background process works enables to adjust the extra write cost versus saved disk space compromise.