iscsi mount的盘的突然变成read only，在系统日志messages中有下面的记录：
Jun 11 22:05:31 oracle11grestore kernel: Buffer I/O error on device sdd1, logical block 169593217 Jun 11 22:05:31 oracle11grestore kernel: lost page write due to I/O error on sdd1 Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] Sense Key : Not Ready [current] [descriptor] Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] Add. Sense: Logical unit communication failure Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] CDB: Write(10): 2a 00 4e 70 f9 90 00 00 20 00 Jun 11 22:05:31 oracle11grestore kernel: end_request: I/O error, dev sdd, sector 1316026768 Jun 11 22:05:31 oracle11grestore kernel: Buffer I/O error on device sdd1, logical block 164503090 Jun 11 22:05:31 oracle11grestore kernel: lost page write due to I/O error on sdd1 Jun 11 22:05:31 oracle11grestore kernel: Buffer I/O error on device sdd1, logical block 164503091 Jun 11 22:05:31 oracle11grestore kernel: lost page write due to I/O error on sdd1 Jun 11 22:05:31 oracle11grestore kernel: Buffer I/O error on device sdd1, logical block 164503092 Jun 11 22:05:31 oracle11grestore kernel: lost page write due to I/O error on sdd1 Jun 11 22:05:31 oracle11grestore kernel: Buffer I/O error on device sdd1, logical block 164503093 Jun 11 22:05:31 oracle11grestore kernel: lost page write due to I/O error on sdd1 Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] Sense Key : Not Ready [current] [descriptor] Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] Add. Sense: Logical unit communication failure Jun 11 22:05:31 oracle11grestore kernel: sd 36:0:0:1: [sdd] CDB: Write(10): 2a 00 56 fa db e0 00 00 10 00 Jun 11 22:05:31 oracle11grestore kernel: end_request: I/O error, dev sdd, sector 1459280864
syslog中有
Jun 11 22:05:58 INFOSEMPER1 kernel: [26052423.897566] Unable to locate Target IQN: iqn.2019-02.com.scutech:555cb1 in Storage Node Jun 11 22:05:58 INFOSEMPER1 kernel: [26052423.903214] iSCSI Login negotiation failed. Jun 11 22:05:58 INFOSEMPER1 kernel: [26052423.908367] iSCSI Initiator Node: iqn.1994-05.com.redhat:1df102341c1 is not authorized to access iSCSI target portal group: 1. Jun 11 22:05:58 INFOSEMPER1 kernel: [26052423.918930] iSCSI Login negotiation failed.
经过分析，可能是网络问题，造成挂载盘的IO错误。
红帽文档介绍REPLACEMENT_TIMEOUT https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/5/html/online_storage_reconfiguration_guide/iscsi-replacements_timeout 里面提到默认是120秒，客户是万兆网长期挂载，计划建议增加到86400秒，也就是一天。
