NFS未解之谜之IO持续占用问题

某核心交易库，报警IOwait超过30%，看似很普通的一条告警，实则暗藏玄机；登陆主机查看到有很多RMAN备份脚本在跑；

平时不到一小时的任务，跑了6个多小时了。
该备份任务通过nfs挂载的方式，怀疑是nfs有问题，

果然，进入到mount目录，ll都无法正常显示结果，卡住不动，随即到备份服务器上面，也就是nfs server查看有没有异常，发现之前部署的一个监控脚本，在平时load和io都很低。与今天故障时间段不太一样。

返回到备份客户端服务器，ps -ef |grep nfs发现有很多cat进程
[root@trandb1 log]# ps -ef |grep nfs
root 9700 2 0 2017 ? 00:00:00 [nfsv4.0-svc]
oracle 88889 88888 0 10:05 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190619_9868_1
oracle 90224 90223 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9888_1
oracle 90566 90565 0 10:06 ? 00:00:00 cat ./nfs/full_data_TRANDB_20190619_9872_1
oracle 90571 90570 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190619_9869_1
oracle 90576 90575 0 10:06 ? 00:00:00 cat ./nfs/full_data_TRANDB_20190619_9872_1
oracle 90584 90583 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190619_9868_1
oracle 90588 90587 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9884_1
oracle 90593 90592 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9885_1
oracle 90597 90596 0 10:06 ? 00:00:00 cat ./nfs/full_data_TRANDB_20190619_9865_1
oracle 90606 90605 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9881_1
oracle 90616 90615 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190619_9871_1
oracle 90626 90625 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9887_1
oracle 90631 90630 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9888_1
oracle 90641 90640 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190619_9871_1
oracle 90645 90644 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9880_1
oracle 91999 91998 0 10:06 ? 00:00:00 cat ./nfs/full_data_TRANDB_20190620_9883_1
oracle 92488 92487 0 10:06 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190620_9880_1
oracle 93837 93836 0 10:07 ? 00:00:00 cat ./nfs/arch_TRANDB_20190620_9890_1
oracle 94011 94010 0 10:07 ? 00:00:00 cat ./nfs/full_data_TRANDB_20190620_9886_1
oracle 94238 94237 0 10:07 ? 00:00:01 cat ./nfs/full_data_TRANDB_20190619_9865_1
root 98024 17863 0 10:09 pts/7 00:00:00 grep nfs
root 130976 2 0 2017 ? 00:00:00 [nfsiod]

通过操作系统kill掉这些pid，但是立马就会派生出来。后umount掉目录后，没有了。暂时没有找出原因，记录一下。