Google cloud VM reboot and data loss of attached persistent disk

0
votes

This is the situation: I hooked a disk to a VM. Reboot the VM (for any reasons). I have to remount the disk otherwise it is not available (unmounted) after the restart. So I remount the disk with the following command: sudo mount -o discard, defaults /dev/[DEVICE_ID] /mnt/disks/[MNT_DIR]

Does the fact that I have to remount the disk also mean that I have lost all the data inside?

Thanks in advance

3
google-cloud-platformvirtual-machinegoogle-compute-enginemount
No. Review how mounting partitions works in Linux., landoflinux.com/linux_fstab.html - John Hanley
... and to add to what Mr Hanley says ... make sure that when you say "persistent disk" you do mean "persistent disk". There is a flavor of disk that can be attached to compute engines called "Local SSD". This type of disk IS persisted across a VM reboot but is NOT persisted across a VM instance stop and restart ... cloud.google.com/compute/docs/disks/local-ssd#data_persistence - Kolban

3 Answers

0
votes

Thanks a lot for your answers. I'm sorry for my question that's not complete. I'm developer and I new in sysadmin.

As you can see here, I added "zonal persistent disk" (type permanent ssd disk) to my VM on Compute Engine (https://cloud.google.com/compute/docs/disks/add-persistent-disk).

Here says if I have a schedule snaphots it's no possible set automatically mount the disk to my VM after restart (that I may need for any reasons). So the question: how I sure that the restart, in addition to unmount the disc, it won't lose the data?

Having disk snapshots I would still be able to restore the data, but I would still understand what happens in this case. Meantime I read your suggestions on linux mount and I have understand that I will not lose the data on the disk with restart of the machine.

Thanks

0
votes

The document that you shared with us says: "If you detach this zonal persistent disk or create a snapshot from the boot disk for this instance, edit the /etc/fstab file and remove the entry for this zonal persistent disk"
Therefore, if you are not creating snapshots from the BOOTDISK you can reboot your instance without having any issue with your data.

However, if you are using snapshots or schedule snapshots of your SSD disk, I would recommend you to follow these best practises to create it : https://cloud.google.com/compute/docs/disks/snapshot-best-practices

But also you can do persistent disk snapshots at any time without unmounting your disk. These recommendations are only in order to have a greater reliability and create the snapshots more quickly (this is also explained in the documentation: https://cloud.google.com/compute/docs/disks/snapshot-best-practices#prepare_for_consistency)

0
votes

In the document that you linked, there is a description of how to add your mount point to /etc/fstab. Using the command line sudo mount -o ... mounts the disk temporarily, but the mount will be lost across reboots. Editing the /etc/fstab will cause the mount point to persist across reboots because that file is read during startup.