I have a two server memcached setup. When memcached write fails, I receive an email notification. About once per day "SERVER HAS FAILED AND IS DISABLED UNTIL TIMED RETRY" error comes and I have no idea how to find the reason.

I am using PHP Memcached client.

I am not using too long keys. I tried adding -v flag, but it does not help, the log remains empty.

If I include output of getStats to the error notification, I receive the following info:

Array
(
    [192.168.0.3:11211] => Array
        (
            [pid] => 28167
            [uptime] => 3671962
            [threads] => 4
            [time] => 1358714713
            [pointer_size] => 64
            [rusage_user_seconds] => 24516
            [rusage_user_microseconds] => 130981
            [rusage_system_seconds] => 86246
            [rusage_system_microseconds] => 675512
            [curr_items] => 1616352
            [total_items] => 118339822
            [limit_maxbytes] => 2684354560
            [curr_connections] => 8
            [total_connections] => 78108681
            [connection_structures] => 356
            [bytes] => 981522779
            [cmd_get] => 1561752945
            [cmd_set] => 158718324
            [get_hits] => 1383072575
            [get_misses] => 178680370
            [evictions] => 0
            [bytes_read] => 138113231690
            [bytes_written] => 1091741700765
            [version] => 1.4.15
        )

    [192.168.0.4:11211] => Array
        (
            [pid] => -1
            [uptime] => 0
            [threads] => 0
            [time] => 0
            [pointer_size] => 0
            [rusage_user_seconds] => 0
            [rusage_user_microseconds] => 0
            [rusage_system_seconds] => 0
            [rusage_system_microseconds] => 0
            [curr_items] => 0
            [total_items] => 0
            [limit_maxbytes] => 0
            [curr_connections] => 0
            [total_connections] => 0
            [connection_structures] => 0
            [bytes] => 0
            [cmd_get] => 0
            [cmd_set] => 0
            [get_hits] => 0
            [get_misses] => 0
            [evictions] => 0
            [bytes_read] => 0
            [bytes_written] => 0
            [version] => 
        )

)