The Root Filesystem Turns Read-only With I/O errors On An OCI Instance Running Ubuntu 18.04
An Oracle Cloud Infrastructure (OCI) Instance running Ubuntu 18.04 as its operating system experiences its root filesystem turning read-only with I/O errors. The root filesystem is on an iSCSI volume.
An OCI instance running Ubuntu 18.04 can experience its root filesystem turning read-only, with the following kinds of I/O errors being logged to the storage volume being used for the root filesystem in the instance's syslog or /var/log/messages log file:
[1823765.929408] sd 3:0:0:1: [sdb] tag#0 FAILED Result: hostbyte=DID_IMM_RETRY driverbyte=DRIVER_OK
[1823765.929411] sd 3:0:0:1: [sdb] tag#0 CDB: Read(10) 28 00 00 13 b7 68 00 00 08 00
[1823765.929413] print_req_error: I/O error, dev sdb, sector 1292136 <<<<<<<<<<<<<<
The volume used by the root filesystem is attached to the instance using iSCSI. iSCSId is disabled by default in the October release of the Oracle-provided Ubuntu 18.04 image, so instances using this operating system may experience a system hang or I/O errors if there is a momentary break in iSCSI communication between the instance and the iSCSI storage unit.