I am in the process of moving some Linux servers onto a virtualized environment with their filesystems mounted from LVM volumes, which are in turn hosted on a remote NAS via iSCSI. I am able to start them up and they run perfectly with no issues.
However, the NAS server is Windows-based and, when Microsoft issues patches, it automatically applies them and reboots. When it reboots, all of the virtual servers' filesystems detect errors and go into read-only mode. I have attempted to remount them as read/write, but the kernel has the filesystem flagged as write-protected, so this fails. The only way I've been able to find to recover is to shut the virt down, fsck its LVM volume, and restart it.
The virts mount these LVM volumes with an fstab entry of the form:
/dev/xvda2 / ext3 noatime,nodiratime,errors=remount-ro 0 1
/dev/xvda2 / ext4 errors=remount-ro 0 1
The virtual host OS also has an LVM/iSCSI mount from the NAS server (in the same volume group, even) which continues working in read/write mode despite these interruptions. Its fstab entry is:
/dev/mapper/nas6-dom0 /mnt/nas6 ext4 _netdev 0 0
This leads me to suspect that removing
errors=remount-ro from the guests' fstab entries would provide fault-tolerance, but I'm a bit uneasy about doing that - if an actual error develops in the filesystem, I would expect that allowing continued writes to the fs could make things much worse in short order.
What is the best practice for resolving this such that the virtual guests will be able to continue running after the NAS reboots itself?