VMworld 2017 Roundup: Day 5

vSAN 6.6: A Day in the Life of an I/O [STO1926BU]

The last(!) session attended at VMworld was presided over by John Nicholson and Pete Koehler. John explained how the vSAN datastore is an object store. It allows for granular availability and can meet business performance requirements. Each object in the object store is made up of one or more components. Data is distributed across the vSAN cluster based on the defined VM storage policy, which means you have some control over how distribution is handled.

The typical objects are:

  • VM home (core VM configuration, i.e. the vmx file),
  • VM swap (note that it’s reserved by default out-of-the-box), and
  • Virtual disk (VMDKs).

Make sure that your vSAN is designed to take advantage of fault domains. You can create fault domains to increase availability within your vSphere/vSAN cluster. Fault domains help protect your environment against such infrastructure related issues like rack failures. An example given was how fault domains could be designed and implemented to make sure the cluster can tolerate a single rack failure.

Fault domains can be extended into nested fault domains for vSAN stretched clusters. Nested fault domains provide redundancy both locally and across sites. vSAN is smart enough that it will leverage the nested fault domain design to reduce I/O between sites, preferring local data to that at another site.

As the session was quite technically dense, here are a few points gleaned from the rest of the presentation:

  • vSAN caches data based on the frequency of data access and data locality.
  • vSAN leverages checksums and disk scrubbing for maintenance.
  • vSAN provides deduplication and compression (note that you need vSAN Advanced or Enterprise for this).
  • Dedupe and compression effectively happen during the transition of data between the caching and capacity tier. Not strictly in-line, but very close and provides more benefits around workload performance impacts.

Pete Koehler also discussed vSAN backend storage I/O, which was a little over my head, especially on the last day of the conference.

If you’re interested at all in how vSAN does what it does, I highly recommend you watch this session once it becomes available online.

Now It’s Time to Say Goodbye

As always, saying goodbye to VMworld is tough. There was so much learned this week, so many folks caught up with, so many steps put on pedometers. It was wonderful. It was exhausting. I’d do it all over again. Until next year, ciao!

Dee Abson

Dee Abson is a technical architect from Alberta, Canada. He's been working in the field of technology for over 20 years and specializes in server and virtualization infrastructure. Working with VMware products since ESX 2, he holds several VMware certifications. He was awarded VMware vExpert for 2014-2020. You can find him on Twitter.

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