96 lines
4.2 KiB
Markdown
96 lines
4.2 KiB
Markdown
[[!meta title="Treat Virtual Machines like Hardware"]]
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This report is based on my experiences as a system engineer,
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who learned a sensible way to run small to large infrastructures:
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Consistent.
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## Appeal
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Treat virtual machines like hardware - this is an appeal to everyone
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in the virtualisation area (providers, vendors, sysadmins, name it).
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Before I go into detail, let me first explain you the situation.
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## Once upon a time...
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... virtualisation was new and slow. [[!qemu]] was the only
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emulator that was kind of usable. Slow, but working. Then,
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some time later, the CPU vendors began to add support for virtualisation
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in hardware and soon virtual machines were kind of running smoothly.
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Xen and VMWare appeared and took their share in the market, while qemu
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had its closed source driver, kqemu.
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Then light virtualisation began its time with software like
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[[!uml]] and OpenVZ. All of sudden somebody propagated the buzzword
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cloud and with it the use of virtualisation spread, as well as the
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problem I am adressing in this article:
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## Virtualisation is treated differently to hardware
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With mass building virtual machines, new problems have risen:
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How to manage those virtual machines? How to manage the networks?
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What about their IP addresses? Where to store, define and assign them?
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What are the virtual properties of the VM? How many disks, how much memory and
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how many cpu (cores) are utilised?
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To solve these problems, specialised tools like
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[[!libvirt]], [[!openstack]] and many other are deployed.
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Problem solved?
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## Problem created: (D)RY
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Interestingly, au contraire de common belief, with inventing tools specific to
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virtualisation management, new problems have been created:
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The domain specific tools can only be used for management of VMs
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(sic!) and thus require the sysadmin to learn a new tool with different
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characteristics from existing tools to manage hardware (I am excluding the effort to run
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and maintain a second tool, because I assume in a automated environment this is negligible).
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So instead of using the existing tools, the [[!dry]] was violated.
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You may claim that virtual machines are different from hardware and thus require
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a different utility, but ...
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## ... Virtual machines are made to closely resemble hardare
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Indeed, the idea of virtual machines is that
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***a virtual machine should behave like its hardware equivalent***.
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As such I postulate
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Treat virtual machines like real machines
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Some of you may now be wondering, ...
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## ... How to treat VMs and hardware the same
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In my opinion (I believe in the [[!kiss]]), managing large scale infrastructures can be as easy
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as managing small infrastructures - given you take the right approach. From a technical
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point of view, to manage an infrastucture you need
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* an inventory management tool (like [[cinv|software/cinv]]) that
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* is the central tool to record all your hosts
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* defines IP address mapppings (mac<->ip, f.i. [[!dhcp]] and ip<->name, like [[!dns]])
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* assists you with lifecycle management of your hosts
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* a configuration management system (like [[cdist|software/cdist]]) that
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* realises your centrally defined configurations
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* manages all your configurations (including VMs!)
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## Summary
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So why treat virtual machines like hardware? Because they can easily be managed the same way
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and they are supposed to very very similar.
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We at [[!ungleich]] take this approach for every infrastructure of our customers
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and so far succeed very well with this approach. We do in fact eat our own dogfood
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and manage the inventories of our customers (HW and VM!) with [[cinv|software/cinv]]
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and configure their infrastructures with [[cdist|software/cdist]].
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To support multiple customers, we keep their configurations under version
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control in different branches using [[!git]] (Logically cdist and
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cdist don't support this, because git can do it much better - we
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follow the [[!unixphilosophy]] when developing software).
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## Future
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There is a lot of work going on at ungleich in the area of virtualisation using
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cdist and cinv. We plan to publish more [!!cdistexamples]] and documentation about
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this soon - so stay tuned if you are interested in seeing the
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***world's simplest virtualisation infrastructure [tm]*** soon.
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[[!tag ungleich vm unix]]
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