+++ This bug was initially created as a clone of Bug #1136201 +++
+++                                                           +++
+++ Please use this bug to backport related fixes to 3.6      +++
+++                                                           +++

The DHT xlator has been fixed in glusterfs-3.6 and several data race issues have been fixed which used to cause data loss during rebalance. With these changes, glusterfs-3.6 and newer clients can correctly co-operate with the rebalance process and not cause any data loss. But clients older than glusterfs-3.6 still have the bugs and could cause data loss when rebalance happens.

To prevent the above, rebalance on glusterfs-3.6 and above need to start only if older clients haven't mounted a volume. The gluster cli needs to warn the user of older clients and fail when attempting a rebalance start. Also, the user should be able to bypass the check using 'force' if needed.

--- Additional comment from Anand Avati on 2014-09-03 07:55:03 CEST ---

REVIEW: http://review.gluster.org/8583 (glusterd: Prevent rebalance starting with old clients) posted (#1) for review on master by Kaushal M (kaushal)

--- Additional comment from Anand Avati on 2014-09-03 11:38:12 CEST ---

COMMIT: http://review.gluster.org/8583 committed in master by Krishnan Parthasarathi (kparthas) 
------
commit 312b339190b7b8f2e38cdd210bf2ee71e53b287e
Author: Kaushal M <kaushal>
Date:   Wed Sep 3 10:50:31 2014 +0530

    glusterd: Prevent rebalance starting with old clients
    
    Glusterd will prevent rebalance from starting when clients older than
    glusterfs-v3.6.0 are connected to a volume. This is needed as running
    rebalance with old clients connected could lead to data loss in some
    cases. The DHT xlator on newer clients (>= 3.6.0) has been fixed to
    prevent the data loss issues.
    
    Change-Id: If58640236382a2fc13f73f6b43777f01713859f7
    BUG: 1136201
    Signed-off-by: Kaushal M <kaushal>
    Reviewed-on: http://review.gluster.org/8583
    Tested-by: Gluster Build System <jenkins.com>
    Reviewed-by: Atin Mukherjee <amukherj>
    Reviewed-by: Krishnan Parthasarathi <kparthas>
    Tested-by: Krishnan Parthasarathi <kparthas>

--- Additional comment from Atin Mukherjee on 2014-09-04 11:45:19 CEST ---

Patch has made into codebase.