migrate data from blob storage on cephfs to s3 online?

[zhucan]

Beacuse of our backend storage is cephfs with replica 3, it need to much storage space to store data; so we want to change the banckend storage from cephfs to s3(EC: 8+2), to reduce storage space waste. is there way to support it?

[milosgajdos]

You can use something like https://github.com/google/go-containerregistry/blob/main/cmd/crane/doc/crane.md to copy the data over, but you'd have to mark the source read only before the data is copied over to the new storage backend.

[zhucan]

only support offline? @milosgajdos

[milosgajdos]

Can you define what you mean by "online"? Do you mean by that that the registry is accepting writes whilst you are migrating data into new storage? This won't be ideal, will it.

Data migrations are hard. If you want make sure consistency between the two data stores, you need to make one as read-only, copy the data over to the new one and then switch over. Otherwise you might find yourself in the situation where some data is in X and not in Y.

[zhucan]

because there is so many data on the storage, we can only accept stop taking service briefly, so whether it's possible copy the data from src to des not mark the src to read only, after most of part data was copied, now top the server, then run copy again to migrate the the latest data?

[milosgajdos]

you can try doing that somehow but it's going to be painful. I've never done that myself.

[zhucan]

thanks, I will try it.