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some thoughts on storage in virtualisation November 15, 2012

Posted by vbry21 in General Stuff.
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Today my mind turns to storage with virtualisation.

I am currently prepping to teach a new virtualisation course and I have just reached the module which deals with storage optimisation.

In the good old days I used to be a virtualisation consultant and engineer. I used to get called out to customer sites to troubleshoot performance issues.

I always followed a specific order in analysing the issue.

1)      Storage

2)      Memory

3)      CPU

4)      Networks

My reasoning being, VMs are stored on datastores, and if we have a great number of VMs on a single LUN / datastore then we have issues.

However other factors need to be considered.

Storage protocols, generally Fibre channel and hardware iSCSI may be faster than software iSCSI and NFS, purely because processing in the software protocols may be done by the host, rather than offloaded to the storage adaptor or array.

Proper Configuration of your storage devices, goes without saying.

Load balancing across storage, generally more read / write heads and multiple paths equals better performance, just think about motorways versus single farm track.

Storage queues, I prefer to call this latency, basically how fast can we eliminate the queue, ideally I’d love a latency of 0ms.

Now obviously I can’t tell you how to configure your storage, but what I hope I’ve given you is some food for thought.

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