Couchbase 2.5 Weird Log Error

Couchbase Server
1

Hi,
I’m using Couchbase : 2.5.0-1059-rel , Single Node
Cluster Size : 52GB
Bucket Size : 52GB
Bucket Usage: 38%

And in somedays, it through some exceptions like this :

** Last message in was refresh_stats

** When Server state == {state,“pool5”,1409479234582,[]}

** Reason for termination ==

** {timeout,{gen_server,call,

                    [dir_size,

                     {dir_size,"/opt/couchbase/var/lib/couchbase/data/pool5"}]}}

[error_logger:error,2014-08-31T17:00:44.605,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:log_report:72]

=========================CRASH REPORT=========================

crasher:

initial call: couch_stats_reader:init/1

pid: <0.6750.115>

registered_name: 'couch_stats_reader-pool5'

exception exit: {timeout,

                    {gen_server,call,

                        [dir_size,

                         {dir_size,

                             "/opt/couchbase/var/lib/couchbase/data/pool5"}]}}

  in function  gen_server:terminate/6

ancestors: ['single_bucket_sup-pool5',<0.20956.5>]

messages: [refresh_stats]

links: [<0.20957.5>,<0.293.0>]

dictionary: []

trap_exit: false

status: running

heap_size: 6765

stack_size: 24

reductions: 3866473856

neighbours:

[error_logger:error,2014-08-31T17:00:44.605,ns_1@127.0.0.1:error_logger<0.6.0>:ale_error_logger_handler:log_report:72]

=========================SUPERVISOR REPORT=========================

 Supervisor: {local,'single_bucket_sup-pool5'}

 Context:    child_terminated

 Reason:     {timeout,

                 {gen_server,call,

                     [dir_size,

                      {dir_size,

                          "/opt/couchbase/var/lib/couchbase/data/pool5"}]}}

 Offender:   [{pid,<0.6750.115>},

              {name,{couch_stats_reader,"pool5"}},

              {mfargs,{couch_stats_reader,start_link,["pool5"]}},

              {restart_type,permanent},

              {shutdown,1000},

              {child_type,worker}]

Can you explain what’s the problem with my Cluster. and how to fix it.
Thank you very much