CentOS

So last thursday, we were doing normal maintenance activities, patching etc... when 2 nodes of a cluster were patched and sent down for reboot. Neither host came back online. I can access them via iLO and I keep getting sent over to a no OS found prompt and it tries to boot from PXE.

I booted to the install disk, and tried to reinstall grub with no change in behavior.

I am trying to not reinstall these hosts as they are very poorly documented, not backed up. And the setup of them is quite complex.

I am looking for any advice on how to restore these hosts to production if at all possible. Thanks.

Boot from the install media in rescue mode and get it to mount the system partitions for the installed system under /mnt/sysimage and explore there.

Been there, done that, bought the T shirt. The big issue is, these are UEFI hosts, and documentation on reinstalling grub on UEFI is a bit sketchy... Been looking, but no joy.

Yes but you need to mount the partitions to look at what's there. For a start is there anything there at all? Is the disk still partitioned? Does it recognise any LVM LVs? Can you run fdisk -lu /dev/sd[a-z] and post the results?