cephFS jewel  client 报警： 

mds0: Client l10－190 failing to respond to capability release

2016-08-26 08:01:49.905823 mds.0 192.168.194.120:6800/171607 3 : cluster [WRN] 7 slow requests, 5 included below; oldest blocked for > 33.942552 secs
2016-08-26 08:01:49.905831 mds.0 192.168.194.120:6800/171607 4 : cluster [WRN] slow request 32.990829 seconds old, received at 2016-08-26 08:01:16.914880: client_request(client.1840252:164888 getattr pAsLsXsFs #1000000760d 2016-08-26 08:01:16.919088) currently failed to rdlock, waiting
2016-08-26 08:01:49.905840 mds.0 192.168.194.120:6800/171607 5 : cluster [WRN] slow request 32.945069 seconds old, received at 2016-08-26 08:01:16.960641: client_request(client.1840252:164889 getattr pAsLsXsFs #1000000760d 2016-08-26 08:01:16.965089) currently failed to rdlock, waiting
2016-08-26 08:01:49.905848 mds.0 192.168.194.120:6800/171607 6 : cluster [WRN] slow request 32.819194 seconds old, received at 2016-08-26 08:01:17.086515: client_request(client.1840252:164893 getattr pAsLsXsFs #1000000760d 2016-08-26 08:01:17.091092) currently failed to rdlock, waiting
2016-08-26 08:01:49.905852 mds.0 192.168.194.120:6800/171607 7 : cluster [WRN] slow request 33.942552 seconds old, received at 2016-08-26 08:01:15.963158: client_request(client.1840252:164835 getattr pAsLsXsFs #1000000760d 2016-08-26 08:01:15.967068) currently failed to rdlock, waiting
2016-08-26 08:01:49.905857 mds.0 192.168.194.120:6800/171607 8 : cluster [WRN] slow request 33.930154 seconds old, received at 2016-08-26 08:01:15.975555: client_request(client.1840252:164836 getattr pAsLsXsFs #1000000760d 2016-08-26 08:01:15.980068) currently failed to rdlock, waiting
2016-08-26 08:01:54.905862 mds.0 192.168.194.120:6800/171607 9 : cluster [WRN] 7 slow requests, 2 included below; oldest blocked for > 38.942642 secs
2016-08-26 08:01:54.905868 mds.0 192.168.194.120:6800/171607 10 : cluster [WRN] slow request 38.920220 seconds old, received at 2016-08-26 08:01:15.985579: client_request(client.1840252:164837 getattr pAsLsXsFs #1000000760d 2016-08-26 08:01:15.990068) currently failed to rdlock, waiting
2016-08-26 08:01:54.905871 mds.0 192.168.194.120:6800/171607 11 : cluster [WRN] slow request 38.894827 seconds old, received at 2016-08-26 08:01:16.010972: client_request(client.1840252:164838 getattr pAsLsXsFs #100

cluster 75f7dde4-d350-4853-9asda6b4ed2
     health HEALTH_WARN
            mds0: Client l10-190 failing to respond to capability release
            mds0: Client l10-191 failing to respond to capability release

问题原因：
    cdn 预取图片回源比较到，导致ngx 进程down 了

解决方法：
    临时解决办法：关闭ngx 服务，重新mont -t ceph *:path

思考：
    1. 视频一当回源将会导致ngx 进程宕机，是否可以改变视频回源，针对视频文件进行切片的大小
       设置，并发数减小
    2. ngx 是否可以优化，改大缓存参数
    3. cephfs 是否可以优化

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cephFs Jewel: mds0: Client failing to respond to capability release 问题分析及思路