I came across that and tried it - the short answer is no, you can't do that
- using cache tier. The longer answer as to why I'm less sure about, but
iirc it has to do with copying / editing the OMAP object properties.

The good news, however, is that you can 'fake it' using File Layouts -
http://docs.ceph.com/docs/mimic/cephfs/file-layouts/

In my case I was moving around / upgrading disks and wanted to change from
unreplicated (well, r=1) to erasure coding (in my case, rs4.1). I was able
to do this keeping the following in mind:

1. The original pool, cephfs_data, must remain as a replicated pool. I'm
unsure why, IIRC some metadata can't be kept in erasure coded pools.
2. The metadata pool, cephfs_metadata, must also remain as a replicated
pool.
3. Your new pool (the destination pool) can be created however you like.
4. This procedure involves rolling unavailability on a per-file basis.

This is from memory; I should do a better writeup elsewhere, but what I did
was this:

1. Create your new pool. `ceph osd pool create  cephfs_data_ec_rs4.1 8 8
erasure rs4.1`
2. Set the xattr for the root directory to use the new pool: `setfattr -n
ceph.file.layout.pool -v cephfs_data_ec_rs4.1 /cephfs_mountpoint/`

At this stage all new files will be written to the new pool. Unfortunately
you can't change the layout of a file with data, so copying the files back
into their own place is required. You can hack up a bash script to do this,
or write a converter program. Here's the most relevant bit, per file, which
copies the file first and then renames the new file to the old file:

func doConvert(filename string) error {
        poolRewriteName, previousPoolName, err :=
newNearbyTempFiles(filename)
        if err != nil {
                return err
        }
        err = SetCephFSFileLayoutPool(poolRewriteName, []byte(*toPool))
        if err != nil {
                os.Remove(poolRewriteName)
                os.Remove(previousPoolName)
                return err
        }

        err = CopyFilePermissions(filename, poolRewriteName)
        if err != nil {
                os.Remove(poolRewriteName)
                os.Remove(previousPoolName)
                return err
        }

        //log.Printf("Copying %s to %s\n", filename, poolRewriteName)
        err = CopyFile(filename, poolRewriteName)
        if err != nil {
                os.Remove(poolRewriteName)
                os.Remove(previousPoolName)
                return err
        }

        //log.Printf("Moving %s to %s\n", filename, previousPoolName)
        err = MoveFile(filename, previousPoolName)
        if err != nil {
                os.Remove(poolRewriteName)
                os.Remove(previousPoolName)
                return err
        }

        //log.Printf("Moving %s to %s\n", poolRewriteName, filename)
        err = MoveFile(poolRewriteName, filename)
        os.Remove(poolRewriteName)
        os.Remove(previousPoolName)
        return err
}



On Wed, May 15, 2019 at 10:31 AM Lars Täuber <taeu...@bbaw.de> wrote:

> Hi,
>
> is there a way to migrate a cephfs to a new data pool like it is for rbd
> on nautilus?
> https://ceph.com/geen-categorie/ceph-pool-migration/
>
> Thanks
> Lars
> _______________________________________________
> ceph-users mailing list
> ceph-users@lists.ceph.com
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>
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