Test / add limited (?) support for s3 disks in ClickHouse

[filimonov]

We need to be sure we do UNFREEZE to release the files which were freezed.

[Slach]

could you explain what exactly you mean?

[filimonov]

I didn't test that (need to be checked) but it looks like that:

If we have s3 disk configured in clickhouse, then freeze command create a 'hardlinks' in shadow dir (both in local FS and in S3) which increment the refcount to the target object.

Even if you remove the file from the local filesystem (or move it to backup subfolder), the 'hardlink' in the virtual filesystem (in s3) stays in place. And it don't allow the data files to be deleted after the part go away (because refcount never goes back to zero).

There is 'unfreeze' command introduced for that (?)

[Slach]

got it

[Slach]

currently when we setup

clickhouse:
  use_embedded_backup_restore: true

s3 disks should be also supported