VSAN Troubleshooting Case Study

vsan-vmware-virtual-san-boxI have been doing a bunch of stuff around disaster recovery (DR) recently, and my storage of choice at both the production site and the recovery site has been VSAN, VMware Virtual SAN. I have already done a number of tests already with products like vCenter Server, vCenter Operations Manager and NSX, our network virtualization product. Next up was VCO, our vCenter Orchestrator product. I set up vSphere Replication for my vCO servers (I deployed them in a HA configuration) and their associated SQL DB VM on Friday, but when I got in Monday morning, I could not log onto my vCenter. The problem was that my vCenter was running on VSAN (a bit of a chicken and egg type situation), so how do I troubleshoot this situation without my vCenter. And what was the actual problem? Was it a VSAN issue? This is what had to be done to resolve it.

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VMworld 2014 – Storage News Part 2

VVolsI guess the next big tech preview at this year’s VMworld was around Virtual Volumes. Yes, we’ve done this before, but this year there were so many vendors showing demos of their VVol implementation, and so many presentations/sessions on the topic that I believe folks are beginning to realize that we are very close indeed to finally having this feature ready. It’s hard to believe that this was first discussed at VMworld 2011, and I alluded to this when I presented a VVol session that I co-delivered with the folks from Nimble Storage at this year’s VMworld.

This topic is going to be huge, and it is going to change the way storage is designed for virtualization environments. And I think almost every storage partner I spoke to at the show is on-board. In fact, “The Register” asked the question last month if there was ANY storage vendor that wasn’t doing a VVol implementation?

I’m not going to get into any technical details of Virtual Volumes in this post – there will be lots of time for this later. Instead, I’m going to share how we believe VVols will now enable Software Defined Storage (SDS) for SAN & NAS arrays, similar to how we have achieved this already with VSAN.

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VMworld 2014 – Storage News Part 1

vmworld-2014-active-banner-v4Yesterday was my first day at VMworld 2014. As usual with this event, there are simply so many interesting announcements that it is hard to keep track. However, for me, there were a few things which stood out in the storage space worth calling out. These are specifically VMware focused products and features. I know that many of our partners have also made announcements in the storage space, but for today I concentrated solely on VMware. There are the two that really caught my attention.

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Thin Provisioning Considerations when formatting volumes in a Guest OS

I had this question recently regarding the best way to format volumes in a Windows 2008 Guest OS, and if there were any considerations with the different formatting types on a volume which resides on a thin provisioned VMDK. Just to be certain that what I was stating was actually true, I set up a small test. Bottom line – use quick format when formatting the volume as a normal format will fill the volume, negating the space-saving associated with thin provisioned volumes.

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VSAN Part 24 – Why is VSAN deploying thick disks?

In this post, we talk about a particular behaviour with using the default (or None) policy with VSAN. I have stated many times in the past that when a VM is deployed on the VSAN datastore, it behaves like it is thinly provisioned unless the capability ‘Object Space Reservation’ (OSR) is specified in the VM Storage Policy. The OSR will pre-allocate space on the VSAN datastore for the virtual machine’s storage objects, and is specified as a percentage of the actual VMDK size. However, there is a slightly different behaviour when the default policy is used. Once again, I was in a conversation with a customer who stated that when he used the default policy of “None”, he could see space being consumed on the VSAN datastore was equal to the size of the VMDK * FTT (Number of Failures To Tolerate). He wondered why this was the case when the default policy clearly did not contain an Object Space Reservation capability.

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VSAN Part 23 – Why is my Storage Object Striped?

Those of you familiar with VSAN will know that one of the capabilities which can be placed in a VM Storage Policy is Number of Disk Stripes Per Object (stripe width for short). I covered this in an earlier post which looked at the various VSAN capabilities. Recently, a customer who had not specified a stripe width in the VM Storage Policy was perplexed to find that his storage objects had indeed been striped across a number of disks. He reached out to me if I could provide an explanation.

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VSAN Part 21 – What is a witness?

At this stage, VSAN has only been in GA for a number of weeks, even though many of us here at VMware have been working on it for a year or two (or even more). Sometimes when we get into explaining the details of storage objects, components, etc, we forget that this is all so new for so many people. In a recent post, someone asked me to explain the concept of a witness on VSAN. Looking back over my posts, I was surprised to realize that I hadn’t already explained it. That is the purpose of this post – explain what a witness disk is in VSAN, and what role it provides.

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