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Migrating from Linode to Hetzner


I've had Linodes running for 4 years. I like Linode, and there are some good reasons to stay.

  • Fast network, and decent disk I/O performance for a VPS. CPU power isn't bad either.
  • Extremely reliable — in the London and East Coast US data centres, and in my experience.
  • Regular service upgrades — disk space, CPU, and most recently RAM — for everyone, including current customers.
  • Famously responsive and helpful support. (Which I barely ever need).
  • Easy-to-use web interface and web-based console.
  • Up-to-date and pretty wide selection of distros.

But recently, I've been thinking about moving services to Heroku or Hetzner.

  • Heroku should be dearer but easier. Moving to Heroku would mean largely giving up on sysadmin, allowing it to take more of my money and not much of my time.
  • Hetzner should be cheaper but (a bit) more time-consuming. Moving to Hetzner would mean embracing sysadmin, continuing to become better at it, and allowing it to take a little more of my time and less of my money.

Linode feels in some ways like an unhappy compromise between these two options. I have to do almost as much sysadmin as I would for a dedicated Hetzner box running Xen. And I have to pay not so far off what it would cost me to give up sysadmin almost entirely on Heroku.

Then, there are a couple of specific reasons I might switch away from Linode.

  • Memory. My Linodes run various web apps which are basically interfaces to a Postgres database. Performance is thus constrained more-or-less exclusively by RAM. As long as my database fits in disk cache, things are snappy. As soon as Postgres has to start hitting the disk, we have a problem. The recent RAM doubling is a big help here. However, cost per GB of RAM is still pretty high, which means I'm running with less than I'd like.
  • Security. The incidents of the past few days have cast some doubt on Linode's security competence and transparency. This is a serious worry.

There are also some specific reasons that have been keeping me off Heroku and Hetzner.

  • Heroku's not-so-intelligent routing shenanigans have slightly tarnished their appeal.
  • With Hetzner, my main worry is disk failure. Sure, you get two disks and can set them up in RAID1 with mdadm. But identical disks are liable to fail close together, and I don't look forward to using mdadm in anger with the clock ticking and my data at risk. Linode and Heroku deal with redundant storage transparently, and I think I trust them to do it right.

I still haven't decided what to do in the long run. If I were going to use Hetzner for production, I'd go for one of the machines with 16GB or 32GB ECC memory. But meanwhile, I got a 4GB server for about €25/month in Hetzner's ongoing auctions, and have been experimenting with moving Linodes to my own Xen setup on this dedicated machine.


What's really nice about this, in theory, is that you can install Xen on your Hetzner box, then transfer your Linode disk images directly and boot them up with minimal downtime and few additional deployment steps.

(I realise that this isn't such an advantage for everyone: if you have some sort of push-button deployment set-up, say with Chef or Puppet, moving hosts is probably no big deal. To date, though, I haven't invested the time and effort to do things this way. I have a small number of systems, of varying ages, manually set up and configured. One of these days, I'll get round to learning Chef, Puppet, or similar. But even when I do, it's not going to help much with these legacy systems. Hence, this direct transfer of disk images is really appealing to me.)

However, it turns out that the Xen documentation, official and otherwise, is less than ideal. It is, variously, non-existent, inconsistent, contradictory, and just plain bad. It thus took me a few days' wrestling to make the transfer from Linode to Hetzner work, for reasons mostly to do with networking. And I therefore thought these steps might be worth sharing.

So, with that out the way, let's proceed to the instructions.