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I am currently tasked with evaluating VSphere and VCenter server. I read about the VMotion feature:

http://www.vmware.com/files/pdf/VMware-VMotion-DS-EN.pdf

This could come in very handy for us. We are always migrating VM's in our current infra. My question is, how well do these "no downtime" migrations work when it comes to databases such as served with MySQL? Do they truly migrate without issue? I can't seem to find much information one way or the other.

Jafo
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  • `Do they truly migrate without issue?` - Please expound on the specific "issues" you're referring to and concerned with. – joeqwerty Sep 17 '15 at 21:32
  • Will the database stop responding during migration, will there be data loss, queued connections, etc.. – Jafo Sep 17 '15 at 21:36
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    It works great. This is a core and key feature of VMware and vMotion. – ewwhite Sep 17 '15 at 21:37
  • Live migration works fine for smaller databases, but becomes problematic for larger databases or databases. Can you imagine live-migrating 4TB worth of data? Even the deltas could be quite large. It can work, and people do it, but you'll need to put a lot of thought into the architecture. Most other shops seem to use another form of HA. – Stefan Lasiewski Sep 17 '15 at 21:54
  • What about databases under 50GB? – Jafo Sep 17 '15 at 21:58
  • If you're running vSphere 6, the enhancements to VMware FT might be worth a look - http://www.vmwarearena.com/2015/02/vsphere-6-0-whats-new-in-vmware-fault-tolerance-ft.html – joeqwerty Sep 17 '15 at 21:59
  • Databases under 50GB might be fine. It really has more to do with the rate of change, and can VMware live migration keep up. Doing a "FLUSH TABLES WITH READ LOCK;" would reduce the rate of change and really help with any migration, but that means that the database is read-only for a period of time. – Stefan Lasiewski Sep 17 '15 at 23:54
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    It think it should be important to know which feature you are realy talking about: vMotion is just moving the vm from one host to another - in fact it is just moving the content of ram. Storage vMotion is moving the vm files from one datastore to anoter. – Tobias Sep 21 '15 at 09:56

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