Persistent disk identifiers

[Mark Woodbridge]

We mount all our additional persistent disks in `/etc/fstab` using `/dev/disk/by-id/google-[DISK_NAME]`, as recommended on this page https://cloud.google.com/compute/docs/disks/add-persistent-disk.

However, having just rebooted our server, all these symlinks have changed to `/dev/disk/by-id/scsi-0Google_PersistentDisk_[DISK_NAME]`. This obviously prevents them from being mounted - which is a big problem. Is this to be expected, or documented anywhere? We're on CentOS 6.

[George (Google Cloud Support)]

Hello Mark,

I wasn't able to reproduce using the CentOS 6 image x86_64 built on 2016-07-11. The disk survived a reboot and I was able to access the mounted location and the df -h is showing the mounted disk.

Is it possible to provide me with the image build that you are using? Did you try using the latest image build?

Looking forward to your reply.

Sincerely,

George

[Paul Nash]

Hi Mark,

I checked with our guest OS engineering team, and they said that mounting the volumes by UUID should get you around issues like this. I'm not totally familiar with the procedure myself, but there are many references.

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[Mark Woodbridge]

Thanks George. These machines were provisioned about 2 months ago using the public CentOS 6 and 7 images.

I can confirm that the /dev/disk/by-id/google-[DISK_NAME] symlinks are missing on all the machine that I have rebooted, and have not returned following subsequent reboots, or when attaching new disks. I'm aware of the workarounds (such as mounting using UUID, or by the scsi-0Google_PersistentDisk symlinks), but the obvious concern is that having following the instructions for attaching persistent disks we were left with machines that failed to boot due to the missing symlinks.

Mark.

[Paul Nash]

Hi Mark,

FYI we've been having an ongoing discussion about this in the engineering team, and hope to determine the cause of the unexpected change, above and beyond the workarounds we mentioned. Someone may reach out to you directly if we need to get more information about this issue. Sorry that it happened, and thanks for reporting it here.

Thx,

-P

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[Mark Woodbridge]

Thanks Paul. Last night's updates have resolved the issue.

Mark.

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Mark Woodbridge
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Chaser
www.chaser.io
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